After Zach Orr announced on Wednesday that he will be pursuing a comeback just months after retiring because of a “career-ending” congenital spine issue, a lot of eyebrows were raised. How could someone who had been told by doctors that he could no longer play football without an increased risk of paralyzation or death reverse course just months later? Are these new doctors being irresponsible with their diagnosis? Will Orr even pass a physical from any NFL teams?

A lot of those questions will continue to persist while Orr visits several interested teams—starting with the Detroit Lions on Thursday—but one prominent former NFL doctor threw in his two cents this week.

Dr. David J. Chao penned an article on Thursday entitled “Zach Orr should play again relatively worry free.” Throughout the article, he notes how common it is for two doctors to have completely differing opinions on a medical condition. As for Orr’s specific ailment, Chao says, “Players have played with an incompletely formed C1 arch. There are likely several current players unknowingly playing with the issue.”

Chao does admit, however, that with any high cervical injury, the risks are extremely serious. “The danger with any high cervical injury is more than potential paralysis,” Chao wrote. “If the spinal cord is injured there, it could cause a person to stop breathing.”

But still, Chao concludes that if this congenital issue is Orr’s only current ailment, “it is likely Orr will be cleared by a team (or teams) to continue playing.”

It is worth mentioning Chao’s checkered background when taking into account his opinions. Chao has made a name for himself as the “ProFootballDoc” on Twitter, providing backgrounds for diagnoses and recovery time for football injuries as they happen in real time. Chao served as the Chargers team doctor from 1997 to 2013, but his time there is marked with troubling accusations and a handful of lawsuits. According to the San Diego Union Tribute, Chao has been sued for malpractice 20 times since 1998. At one point, the NFLPA called for him to be fired because of the increasing malpractice lawsuits. When Chao finally stepped down in 2013, Chargers fans “rejoiced.”

But Chao has remained a somewhat reliable source on injury diagnoses in his post-NFL career. His opinion on Orr, like any physician, is just his. Other NFL doctors, like the Ravens medical team that suggested Orr end his football career, may see things differently. With the Lions likely going through medical tests with Orr on Thursday, we’ll see what the future holds for the All Pro linebacker.