According to assistant GM John Ricco, Mets INF Wilmer Flores has a "disc" issue which is causing the soreness in his lower back.
The Mets announced on Monday that Flores hit the 10-day DL with a sore lower back. He had to leave Sunday's game after feeling lower back soreness, and manager Mickey Callaway said that he had been battling that injury last week as well. Flores traveled back to New York to have his back examined.
Flores has been playing third recently with Todd Frazier on the DL himself with a hamstring injury. Luis Guillorme, who replaced Flores at third on Sunday, could be the next-best option with Jose Reyes on the bench as well.
This season, the 26-year-old is hitting .248 with three homers and 13 RBI over 46 games.