NEW YORK — Second baseman Neil Walker will likely opt for season-ending surgery on a herniated disc in his back, Mets manager Terry Collins announced following New York’s 5-2 victory over the Miami Marlins at Citi Field on Wednesday.

“After all the evidence has been gathered, he thinks that’s where he’s probably headed,” Collins said.

Walker is expected to address the media Thursday.

Already without Matt Harvey (thoracic outlet syndrome) for the remainder of the year and with lingering injuries to Noah Syndergaard (bone spur), Steven Matz (shoulder/elbow), Asdrubal Cabrera (knee) and Yoenis Cespedes (quad), losing Walker comes at an inopportune moment. The Mets have won 10 of their last 13 to close to within 1 1/2 games of St. Louis for the second National League wild card.

“This year, Walker has been a big part of this team, it’s a shame,” infielder Wilmer Flores said. “We’ve had a lot of injuries but we have to keep playing with what we have.”

Flores and Kelly Johnson, who both homered in New York’s victory, stand to see increased playing time over the final 29 games of the regular season in Walker’s absence.

“Massive,” Johnson said about how big of an impact losing Walker for the remainder of the season would be. “Losing anybody that you’ve been counting on and having such a great year, not just on the field but in here. Hopefully he’ll be around regardless of what happens. We’re going to miss him a lot and hopefully we can pick him up.”

Both Walker and the Mets had previously classified the injury as a stiff back. Collins indicated he wasn’t at liberty to reveal the exact diagnosis during Tuesday’s pre-game news conference, but general manager Sandy Alderson shared the condition to a few reporters early Wednesday afternoon.

Collins was then pressed for additional details before the Mets took on the Miami Marlins.

“The issue is, the herniated disk is causing weakness in one of his legs,” Collins said before the game. “The weakness is causing numbness in one of his feet. The numbness is keeping him from playing.”

Walker has matched his career high with 23 home runs in his first season with the Mets.

“We’re certainly very disappointed that it comes to this,” Collins reflected. “He’s had a tremendous year for us.”

Walker’s 2012 season with Pittsburgh ended prematurely with a similar injury. He went through six weeks of physical therapy to rehabilitate a disk in his lower back.