Jeremy Hefner announced via Twitter this morning that he would undergo Tommy John surgery. This will be his second time undergoing the operation. Hefner spent parts of two seasons with the Mets. He mostly filled the role of spot starter and long reliever. In his 50 appearances, he had a 4.65 ERA and 4.49 FIP. In terms of WAR, Fangraphs has him just above replacement level, while Baseball Reference has him just below replacement level.
Hefner's last Tommy John surgery took place in late August of 2013. Since then, he had been on the rehab trail making appearances with the Mets’ rookie and High-A affiliates. This was going on until it was announced that he had suffered a significant setback.
For Hefner, this is a significant blow towards his quest to return the big leagues. For the Mets, however, it is less of an issue because of the team's pitching depth. Even if Hefner had been able to return by the start of next season, it is unclear if there would have been a spot for him on the Mets' roster.