3:24pm: Surgery is an option for Walker, despite Alderson’s optimism, Collins told reporters (Twitter links via DiComo). Collins added that the Mets don’t want to put Walker in the lineup until receiving a second opinion on his back (via ESPN New York’s Adam Rubin). And, even if Walker does continue to play for the remainder of the season, Collins stated that Walker would “probably not” be able to play on an everyday basis.

12:21pm: The specific injury that has limited Mets second baseman Neil Walker is a herniated disk in his back, Mets GM Sandy Alderson told reporters including MLB.com’s Anthony DiComo (via Twitter). Alderson reiterated that Walker can play through the injury, which he painted as being somewhat less serious than it had seemed yesterday after comments from manager Terry Collins.

Walker seems to be experiencing problems most directly to his lower body, with the disk issue causing some weakness in his foot per ESPNNewYork.com’s Adam Rubin. That’s something that the veteran has dealt with previously, but he will nonetheless be pursuing a second opinion.

At this point, then, it’s not entirely clear how the problem will impact Walker down the stretch and in his upcoming free agency case. New York’s acquisition of Walker looks even better in retrospect than it did at the time, and he has set himself up for a nice payday with a high-powered season at the plate. But teams weighing lengthy commitments will surely be watching closely to see whether the herniated disk hampers him over the next several weeks.