Our Executive Team

Jane A. Willemsen

Chief Operating Officer
John Muir Health

Jane Willemsen serves as John Muir Health’s first Chief Operating Officer. In her role, she has responsibility for all John Muir Health hospital, physician practice and value-based care operations. In addition to these responsibilities, Ms. Willemsen serves as Governing Board Co-Chair of the highly successful Children’s Specialty Services Partnership, a joint venture with Stanford Children’s Health/Lucile Packard Children’s Hospital.

Before assuming her new position, Ms. Willemsen served as Executive Vice President and President of Hospital Operations for five years and President and Chief Administrative Officer of the Walnut Creek Medical Center for 10 years. Under her leadership, the medical centers achieved numerous quality recognitions, including being named as one of America’s and among the region’s top hospitals by U.S. News and World Report with a nationally ranked service(s) for 15 consecutive years. Both the Concord and Walnut Creek Medical Centers also have achieved Magnet® recognition status for excellence in nursing services and quality nursing care. 

Prior to joining John Muir Health in 2006 as President and Chief Administrative Officer of the Walnut Creek Medical Center, Ms. Willemsen served as Executive Vice President and Chief Operating Officer at Queen of the Valley Medical Center in Napa, California. She also worked at the Rehabilitation Institute of Chicago as Vice President of Nursing and Allied Health and Assistant Director of Nursing. She received a Bachelor of Science degree in Nursing from the University of Iowa, and a Master of Management degree from the Kellogg Graduate School of Management at Northwestern University.

Lisa Foust

Senior Vice President, Chief People and Engagement Officer
John Muir Health

Lisa Foust is Senior Vice President, Chief People and Engagement Officer for John Muir Health. As part of the executive leadership team, she is responsible for human resources strategy, labor relations, benefits design and administration, talent acquisition and performance management. Lisa also oversees employee health management, leadership and organizational development, and volunteer services.

In addition to being the executive sponsor of the Muir Management System and co-executive sponsor of John Muir Health’s High Reliability journey, Lisa leads enterprise-wide employee engagement programs and provides executive oversight of the Belonging and Equity Initiative a comprehensive platform emphasizing diversity, equity and inclusion at John Muir Health.

Prior to joining John Muir Health in 2013, Lisa served for eleven years as Chief Human Resources Officer for Emanate Health (formerly known as Citrus Valley Health Partners), a not-for-profit health system operating three acute care hospitals as well as inpatient and outpatient hospice services in Southern California.

Lisa received a Master of Public Health degree from California State University, Northridge where she also received her undergraduate degree in the field of health science.

Dr. Maureen Stevenson

MD, Chief Administrative Officer
John Muir Health Ambulatory Services and Population Health  

Maureen Stevenson, MD is Chief Administrative Officer for John Muir Health’s Ambulatory Services and Population Health. In this role, Dr. Stevenson has oversight of all practice sites for John Muir Health’s four Foundation Medical Groups (Primary care, Cancer Care, Multispecialty Care and Cardiovascular Care).  She also oversees the System’s Population Health program which includes Ambulatory Care Management, Palliative Care and Diabetes Care.   

Prior to assuming the role of Chief Administrative Officer in October 2024, Dr. Stevenson was Senior Vice President of John Muir Health Foundation Practice Operations and oversaw the operations of all 4 John Muir Health Foundation Medical practices (Primary care, Cancer Care, Multispecialty Care and Cardiovascular Care). In addition, Dr. Stevenson provided administrative oversight of the John Muir Health Diabetes Services, Palliative Care and Home Visit program.

Prior to her role as the Senior Vice President of John Muir Health Foundation Practice Operations she was the SVP she was the Senior Vice President and Chair of Ambulatory for John Muir Medical Group. In this capacity she provided operational oversight of all ambulatory physicians, nurse practitioners and physician assistants working within the John Muir Medical Group primary care offices, urgent care centers and endocrinology offices. In addition, Dr. Stevenson provided administrative oversight of the John Muir Health Palliative Care and Care at Home programs.  

Dr. Stevenson is currently serving on the John Muir Health Value-Based Care Council and has chaired or participated in numerous committees for John Muir Medical Group and John Muir Physicians Network, as well as serving on the Board of Directors for John Muir Medical Group from 2009 to 2012.  

Before joining John Muir Health in 2006, Dr Stevenson practiced Internal Medicine at Virginia Mason Medical Center in Seattle and served as Section Head of one of their satellite Adult Medicine practices.  

Dr. Stevenson received her medical degree from State University of New York, Health Science Center in Brooklyn, New York, and her bachelor’s degree in biology from St. John’s University. She is also an alumnus of the California Healthcare Foundation’s Leadership Fellowship and a Carol Emmott fellow.

Michelle Lopes

RN, MSN, NEA-BC, Chief Administrative Officer
Clinical Integration and Performance and System Chief Nurse Executive
John Muir Health

Michelle is the Chief Administrative Officer for Clinical Integration and Performance and System Chief Nurse Executive for John Muir Health. She is responsible for overseeing clinical integration including care coordination and integrated care models, continuous performance improvement, nursing leadership, nurse workforce management, patient care quality, innovation and patient care best practices.

Michelle began her career with John Muir Health in 1991 as an endocrine staff nurse. Over the years, she has held various leadership roles with increasing responsibilities including Director of Clinical Operations, Director of Women’s and Children’s Services and Chief Nursing Officer for the Walnut Creek Medical Center. In 2018 she advanced to Senior Vice President and System Chief Nurse Executive before assuming her current role in 2024.

In addition to serving as the Chairman of the Board of Directors for Hospice of the East Bay, Michelle is a member of the Association of Nurse Executives (AONE), Association of California Nurse Leaders (ACNL), and East Bay Association of California Nurse Leaders (EBACNL).

Michelle holds a Bachelor of Science in Nursing from Samuel Merritt College of Nursing/St. Mary’s College of California, and a Master of Science in Nursing Administration from California State University, Dominguez Hills. She also holds a Nursing Executive – Advanced certification from the American Nurses Credentialing Center. 

NEVIN E. KESSLER

President, John Muir Health Foundation John Muir Health

Nevin Kessler is President of the John Muir Health Foundation where his role is to build a fundraising organization capable of generating increasing levels of private support to further the important mission of the John Muir Health system.

Among his priorities is the successful launch and completion of the $100 million Campaign to Conquer Cancer. In his first two years leading the John Muir Health Foundation, the organization raised a record-breaking $97 million.

Before joining John Muir Health in 2022, Nevin spent 28 years in leadership roles in higher education advancement. Most recently he served as President of the Rutgers University Foundation where he led the completion of the university’s first $1 billion campaign and planned for the launch of its first multi-billion-dollar campaign. During his seven and a half years at Rutgers, fundraising commitments increased 90% from $132 million in 2013 to $251 million in 2019, setting fundraising records in five out of eight fiscal years.

Nevin also led successful fundraising efforts at North Carolina State University, Yale School of Management, University of Connecticut Foundation, Inc., and Virginia Tech. Nevin serves as the executive sponsor of the LGBTQ+ Employee Resource Group at John Muir Health, and he is a member of the Board of Directors and Chair of the Development Committee for the Diablo Regional Arts Association in Walnut Creek, CA, and has been a frequent presenter at professional conferences on fundraising.

Nevin holds a Master of Arts degree in College Student Personnel from Bowling Green State University, Bowling Green, OH, and a Bachelor of Arts degree in History from Dickinson College, Carlisle, PA. 

Paul Deeringer

Chief Strategy Officer
John Muir Health

Paul Deeringer is John Muir Health’s Chief Strategy Officer (CSO), responsible for developing the health system’s long-term vision and aligning the organization with strategic goals. Paul also serves as JMH’s executive sponsor and/or board member for numerous JMH partnerships and affiliations.

Prior to stepping into the CSO role in December 2023, Paul served as Senior Vice President of Strategy and Emerging Business at John Muir Health for eight years. In this capacity, he had overall responsibility for development and execution of ambulatory physician strategy, and operational accountability for physician-facing business functions.

Before joining John Muir Health, Paul practiced as a healthcare regulatory and transactional attorney at Hooper, Lundy & Bookman, a nationally recognized law firm specializing in serving healthcare providers and suppliers, including healthcare technology startups. Prior to his law practice, Paul worked as a management consultant with McKinsey & Company, focused on payor and provider growth strategy. 

Paul received his bachelor’s degree in religion from Princeton University, and his law degree from Georgetown University with an emphasis in healthcare economics.

Rani Singh

Interim Senior Vice President and General Counsel
John Muir Health

Rani Singh is the interim Senior Vice President and General Counsel for John Muir Health. In this role, Rani is responsible for the provision of legal advice to the governing board and senior management of John Muir Health, John Muir Physician Network, John Muir Behavioral Health and the John Muir Health Foundation. She also has oversight responsibility over Compliance, Internal Audit and Information Security. 

Before Rani assumed her current interim leadership role in December 2024, she served as Associate General Counsel. Her responsibilities included providing guidance and advice on employment and labor matters, litigation oversight, risk and consent issues, clinical research matters, federal and state health information privacy and security and compliance matters.

Prior to joining John Muir Health in 2015, Rani served as Principal Counsel at the University of California’s Office of the General Counsel's Health Law Group. In this capacity, she advised each of the University of California medical centers — UC Davis, UC San Francisco, UC Los Angeles, UC Irvine, and UC San Diego — on a broad range of issues, including federal and state health information privacy and security, compliance, Medicare and Medi-Cal reimbursement, and medical staff matters. Rani also served as an associate in the health law practice at the law firm Sidley Austin Brown and Wood, where she was regulatory counsel to a range of clients, including health systems, medical centers and pharmaceutical companies.

Rani earned her JD from the University of California, Berkeley School of Law in 2005 and holds an undergraduate degree in English Literature and International Relations from Pomona College.

Dr. Russell Rodriguez

MD, Senior Vice President and Chief Medical Officer (CMO)
John Muir Health

Dr. Rodriguez has held numerous medical staff appointments and positions at John Muir Health acute care facilities including many years as the Department Chair for Emergency Medicine, Chair of Emergency Preparedness Committees, and six years in the Chief of Staff progression. He became Vice-Chief of Staff at the Concord Medical Center in 2015, followed by Chief of Staff in 2017 and finally Past-Chief of Staff in 2019. Dr. Rodriguez also served on the John Muir Health Board of Directors during his tenure as Chief of Staff.

In 2018, Dr. Rodriguez led the process to integrate John Muir Health’s two separate Emergency Departments into one cross campus department and he served in the role of Cross Campus Medical Director of the Emergency Department until he assumed the position of CMO. As an active member of the Concord and Walnut Creek Medical Staffs, Dr. Rodriguez works clinically in both Emergency Departments.

Dr. Rodriguez received his medical degree from George Washington University Medical School, where he graduated as a member of the Alpha Omega Alpha Honor Medical Society, and earned his bachelor’s degree in molecular biology from the University of California, Berkeley. After medical school, Dr. Rodriguez returned to the Bay Area where he completed his residency in Emergency Medicine at Stanford.

Zach Harris

Chief Administrative Officer, Ancillary, Emergency and Specialized Care Services
John Muir Health

Zach Harris is Chief Administrative Officer, Ancillary, Emergency and Specialized Care Services at John Muir Health. In this role, Zach leads these areas across three hospitals and nearly 60 clinics, encompassing over 2,100 caregivers.

Prior to joining John Muir health in 2021, Zach led operational strategy for outpatient physician practices at Stanford Children's Health. He also managed ambulatory, clinically integrated network, and Medicare Shared Savings Program strategy and operations at Queen's Health System in Hawaii, focusing on primary and urgent care. Zach also held leadership roles at Hawaii Medical Service Association, Oregon Health and Science University, Children’s Health in Dallas, TX, and the Department of Veteran’s Affairs.

As a rising leader in the healthcare industry, Zach has been recognized by multiple "Forty Under 40" lists, including the Portland Business Journal, Healthcare Innovation, and the Cancer Consortium, as well as one of 42 Rising Stars under 40 in healthcare leadership by Becker’s Healthcare. He is a Fellow of the American College of Healthcare Executives, a Fellow in the American College of Medical Practice Executives and is a certified lean six sigma black belt.

With a firm belief that healthcare is a fundamental human right, Zach is deeply passionate about delivering high-quality and equitable care to communities. He is a published author in the areas of health equity, diabetes incidence in underserved minority populations, the significance of primary and preventive care, healthcare's role in preventing gun violence, sustainability, climate equity and climate resilience.

Zach received both his MBA and MPH degrees from Oregon State University where he also earned his undergraduate degree in Sociology.