Ronan is the Red Sox's medical director and an internist at Massachusetts General Hospital. According to a team spokeswoman, "he has been helping coordinate David's care at MGH."
The latest report on Ortiz's care is encouraging.
"David arrived at Massachusetts General Hospital last night and underwent a successful second surgery," Tiffany Ortiz said Tuesday. "He is stable, awake, and resting comfortably this morning in the ICU, where he is expected to remain for the next several days."
The stakes are far higher now than the last time Ronan oversaw Ortiz's medical treatment. "Big Papi" battled chronic foot soreness during his final season, in 2016.
But Ronan is no stranger to life-and-death situations. He was a Sox team doctor in 2006, when pitcher Jon Lester was diagnosed with non-Hodgkin lymphoma, a blood cancer.
"I watched [Lester] go through diagnosis and treatment, and rebuild his body and recover emotionally," Ronan recalled in a 2014 interview with Harvard Medicine magazine.
The Red Sox declined to make Ronan available for an interview Tuesday.
Ronan also was Sen. Edward M. Kennedy's personal physician and issued public updates throughout the late lawmaker's battle with brain cancer. Boston Globe columnist Adrian Walker profiled Ronan at the time.
"His whole pedigree shows that he's very accomplished and skilled," Dr. John Rich, a medical-school classmate of Ronan's, told Walker. "But those aren't the things that really distinguish a doctor. It's the humanity you bring to your practice."
Two years before Walker's 2008 column, Ronan was featured prominently in a Globe series about the rescue of an Iraqi boy who was mistakenly shot by U.S. troops and subsequently flown to Boston for life-saving surgery. Ronan, who directs a refugee-medicine fellowship program at MGH, coordinated the boy's care.