The Mets suffered another big body blow Wednesday.

Neil Walker will not play again this season. Manager Terry Collins said the second baseman, one of the team’s most consistent run-producers, is opting to have back surgery to address the herniated disc that kept him out of the lineup the past four games.

Walker made this decision after being evaluated by a specialist Wednesday afternoon. He was sent to the specialist because the club was concerned that trying to play would risk further injury. The hope was that he could avoid season-ending surgery and continue a season where he hit .282 with 23 home runs and 55 RBIs.

“We’re certainly very disappointed that it comes to this,” Collins said. “He’s had a tremendous year for us. But certainly he makes the decision and it’s in his best interest.”

“It’s a massive hit, losing anybody that you’ve been counting on and having such a great year,” Kelly Johnson said. “Not just on the field but in (the clubhouse). He’s got a positive attitude, upbeat, has fun, loves playing the game. It rubs off on us . . . We’re going to miss him a lot. Hopefully, we pick him up.”

Walker’s disc issue is causing weakness down one of his legs and numbness in his foot. Collins said before the game that the numbness was the reason Walker wasn’t able to play, and that until they had the opinion of the specialist “we’re hesitant to put him out there.”

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Second base could be manned by a variety of people, including Jose Reyes, Johnson and Wilmer Flores.

Walker joins a long list of key Mets who have been lost for the season. David Wright (back) and Matt Harvey (thoracic outlet syndrome) required surgery, and Lucas Duda hasn’t come back from a stress fracture in his back. Zack Wheeler was supposed to return from Tommy John surgery but had setbacks in his recovery.

“It’s definitely huge. This year, Walker has been a big part of this team,” Flores said. “It’s a shame. But we’ve got to deal with it. We’ve had a lot of injuries and we’ve got to keep playing with what we have.”

This is not a new condition for Walker, who had these same symptoms while with the Pirates. And it bothered him earlier this season.

“It’s been off and on all year. As Neil puts it, he has gritted it out, the discomfort level,” Collins said. “Sometimes it goes up. When it goes back down, he needs rest until the strength comes back up again.”

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Collins said that after a recent game, Walker told him that he was glad it ended in nine innings because he wasn’t sure whether he would have been able to play longer than that.

Walker will be a free agent at the end of the season, but earlier this year it sounded as if the Mets were considering offering him an extension to stay. General manager Sandy Alderson said he planned to reach out to his representatives. Whether his back condition affects the Mets’ position on Walker being part of their future remains to be seen.