NEW YORK -- Seth Lugo, whose rise from 34th-round Draft pick to rotation savior fueled the Mets' postseason run last year, has been diagnosed with a partially torn ulnar collateral ligament in his right elbow, the Mets announced on Tuesday. He received a platelet-rich plasma injection, and he will rest for at least the next two weeks.
The Mets said surgical repair of Lugo's UCL is still a possibility depending on how his treatment goes. 
Lugo, 27, did not make the Mets' Opening Day roster because of discomfort in his elbow. An MRI taken Saturday revealed only inflammation, but the Mets sent Lugo for a second opinion Tuesday in Manhattan. A second round of tests there revealed the UCL tear.
The news is not necessarily disastrous for Lugo, considering the history of players who have pitched through partial UCL tears -- including Yankees star Masahiro Tanaka, who has done so for more than two seasons. But it comes at a time of fragility for the Mets, as their starting pitching depth has evaporated in recent weeks. In addition to Lugo's injury, left-hander Steven Matz is on the 10-day disabled list with a flexor tendon strain, an injury that should cost him at least all of April and much of May.
Matt Harvey, Jacob deGrom and Zack Wheeler are all set to pitch in regular-season games this week for the first time since surgeries. Should anything happen to one of those three, the list of candidates to replace them begins with Rafael Montero and Sean Gilmartin, who posted a combined 7.61 ERA in the big leagues last season.
Had Lugo been healthy, he likely would have made the Mets' Opening Day bullpen. Instead, Montero is in that group, with Gilmartin and Adam Wilk headlining the rotation at Triple-A Las Vegas. The Mets shed multiple starting depth options over the offseason, watching Bartolo Colon sign with the Braves on a one-year deal and trading Gabriel Ynoa to the Orioles for cash.
That left the team essentially seven deep in its rotation, with Lugo one of the seven. A 34th-round pick in 2011, Lugo burst onto the scene last season with a 5-2 record and a 2.67 ERA in 17 outings, drawing rave reviews for a curveball featuring the fastest spin rate in Statcast™ history. But Lugo said recently that he experienced elbow discomfort as far back as last Spring Training.
This March, Lugo joined Team Puerto Rico for the World Baseball Classic, posting a 4.20 ERA in three starts. Between that and Grapefruit League games, he led the Mets with 26 1/3 spring innings.