PORT ST. LUCIE — Taijuan Walker’s right knee might be the biggest threat to the Mets opening the season with their starting rotation intact.

The right-hander underwent surgery to remove damaged tissue in the knee on Jan. 14, according to manager Buck Showalter, and there is “a chance” he will be ready to begin the season.

Later, the team issued a statement saying Walker has been cleared for baseball activity and is throwing off a mound. He will remain in a running progression before he is cleared for full-game activity.

If Walker isn’t ready to start the season it would provide an opportunity for a depth piece such as Trevor Williams, Tylor Megill or David Peterson to join the rotation.

Walker, 29, went 7-11 with a 4.47 ERA in 30 appearances last season for the Mets. After a strong first half that earned him a spot in the All-Star Game, he slumped badly over the final 2 ½ months, pitching a full season for the first time since 2017.

Robinson Cano, returning from a second PED suspension that kept him sidelined for all of last season, spoke to teammates in what could be described as an apologetic gesture, according to Showalter. Last season Francisco Lindor indicated the veteran second baseman would probably have to apologize to teammates upon returning.

“You could tell [Cano] had been waiting for a long time and it was really something he had on his heart,” Showalter said. “The guys were very receptive.”

Starling Marte was sidelined from Monday’s workouts because of left oblique discomfort, according to Showalter. The veteran outfielder — who has a history of oblique injuries — underwent an “imaging” exam and X-rays that were negative.

“We know with that type of area it puts a flag up initially, but so far so good,” Showalter said, adding that Marte notified the Mets about the oblique last week.

Seth Lugo, Yennsy Diaz and Felix Pena still hadn’t reported to camp as of Monday. Lugo had travel problems because of weather and Diaz and Pena were dealing with visa issues, according to Showalter. It’s expected Lugo will arrive before Tuesday’s workouts.