The Mets’ offseason has taken a crushing twist.

Prospect Ronny Mauricio was diagnosed with a torn ACL and will undergo surgery, according to multiple reports.

Mauricio, 22, was injured during a Dominican Winter League game Sunday night when he stopped himself in his tracks during an apparent steal attempt, and video showed Mauricio limping off the field.

Mauricio, the No. 4 prospect in the Mets’ system according to MLB.com, made his MLB debut for the Mets earlier this year, hitting .248 with two home runs, nine RBIs, seven steals and a .643 OPS in 108 plate appearances.

Mets president of baseball operations David Stearns said he wasn’t pursuing external options at third base because he wanted to see what Mauricio, Brett Baty and Mark Vientos could do at the position.