Our Executive Team

Matthew van Leeuwe

Chief Operating Officer
John Muir Health

Matthew van Leeuwe serves as Chief Operating Officer at John Muir Health, where he provides executive leadership across hospital, ambulatory, and system operations. In this role, he oversees key clinical and administrative service lines, advancing high-quality, efficient, and accessible care for the communities John Muir Health serves.

Before joining John Muir Health, Matthew was Chief Administrative Officer at Geisinger Health System in Pennsylvania. There, he led multiple systemwide service lines, including diagnostic medicine, patient placement, telemedicine, behavioral health, senior care, and community medicine, supporting operations across 10 acute care hospitals and more than 200 clinic sites.

Matthew has held senior leadership roles across a wide range of care settings, including Executive Director of Hospital Operations at UC Davis Medical Center, as well as Chief Operating Officer and interim Chief Executive Officer positions at hospitals in Texas. Throughout his career, he has driven operational excellence across academic medical centers, integrated health systems, rural hospitals, and investor-owned organizations, with a focus on service line growth, physician recruitment, patient flow optimization, and performance improvement.

Matthew holds a Master of Science in Health Care Administration from Trinity University and a Bachelor of Arts in Psychology from The University of Texas at San Antonio.

Ted Wang

Chief Financial Officer 
John Muir Health

Ted Wang is Chief Financial Officer for John Muir Health. In this role, he leads all matters related to finance across the health system, including advising and supporting the executive team and Board of Directors. Ted is responsible for ensuring financial rigor and seamless coordination around business plans, pro forma development, and all growth‑related activities. He plays a key role in developing and advancing strategies, while also ensuring standard and accurate reporting capabilities are embedded within John Muir Health.

Prior to joining John Muir Health, Ted served as CFO for UCSF Benioff Children's Hospitals and for Children's Services at UCSF Health. His responsibilities included financial and capital planning, budgeting, financial reporting reimbursement, revenue cycle management, and design and operation of internal control systems. During his tenure at UCSF, he developed a ten-year financial plan, attained UC Regent’s approval for a new Children’s Hospital, secured debt financing, and managed operational performance to ensure ongoing financial sustainability.

Ted earned a bachelor’s degree in economics from the University of California, Santa Barbara and holds a Master of Health Administration degree from Cornell University.

Dr. Russell Rodriguez

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.

Rebekah Martinek-Williams

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

Rebekah Martinek-Williams 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, employee belonging and engagement, and performance management. Rebekah also oversees employee health management, leadership and organizational development, and volunteer services.

Rebekah joined John Muir Health in 2026 from City of Hope in Southern California where she worked at their flagship cancer center as System Vice President of HR Client Services. During her tenure, she helped lead critical system design work as City of Hope advanced toward becoming a unified health care system.

Rebekah believes that when health care organizations invest in employees, support their well-being, and help them grow, they are empowered to provide exceptional patient care. She is committed to championing a workplace where every employee feels valued, supported, and inspired to contribute their best.

Rebekah earned her Bachelor of Arts degree in English Literature from Cal-State Fullerton where she graduated with honors and her Juris Doctor from Whittier Law School.

Scott Gregerson

Chief Strategy Officer
John Muir Health

Scott Gregerson, J.D., is Chief Strategy and Business Development Officer at John Muir Health, where he leads enterprise strategy, business development, partnerships, growth initiatives, and market expansion efforts. He is a seasoned healthcare executive with more than two decades of leadership experience across integrated health systems, physician organizations, and national healthcare services companies.

Prior to joining John Muir Health, Scott served in senior executive roles at Sutter Health, ATI Physical Therapy, Envision Healthcare, Stanford Health Care and Epic Care. Throughout his career, he has led strategic affiliations, mergers and acquisitions, operational turnarounds, physician alignment initiatives, and large-scale growth strategies, with a focus on advancing access, quality, and long-term organizational sustainability.

Scott earned a Juris Doctor from Washington and Lee University School of Law and a Bachelor of Arts from the University of California, Santa Barbara. He is licensed to practice law in California and is a Fellow of The Advisory Board Company.

Sanjib Dutt 

Chief Information Officer  
John Muir Health

Sanjib Dutt is Chief Information Officer for John Muir Health. He serves as the technology executive on the senior leadership team and collaborates with John Muir Health’s Chief Medical Information Officer to ensure Information Technology Services effectively support John Muir Health’s operational and clinical excellence. Sanjib also works closely with Optum Information Technology Services leadership and their support team to ensure prudent planning and effective coordination with this strategic partnership. 

Prior to his current role, Sanjib served as John Muir Health’s Chief Information Security Officer and Director of Internal Audits where he provided ongoing guidance on John Muir Health’s cybersecurity program at a strategic level and ensured that the health system stayed compliant with cybersecurity standards, policies, regulations, and legislation. 

Sanjib earned his undergraduate degree in Mechanical Engineering, a Master of Engineering Sciences degree in Robotics and Computer Aided Design from Lamar University and a Master of Business Administration in Finance from the University of Southern California. 

Nevin E. Kessler

President, John Muir Health Foundation
Senior Vice President, Philanthropy 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.

In his first three years in this role, he led the Foundation’s successful launch and completion of the $100 million Campaign to Conquer Cancer, raising $137.9 million at its completion in December 2024. During the same period, the Foundation transferred a record $55.6 million to support John Muir Health’s mission of providing exceptional and compassionate care to the residents of its service area.

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 is a member of the Board of Directors, as well as Chair of the Development Committee, for the Diablo Regional Arts Association in Walnut Creek, CA.

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.