Lugo had a platelet-rich plasma injection Tuesday at the Hospital for Special Surgery and will not throw for about two weeks. The teams said he then will start a throwing program and that the need for surgery will be determined based on how he feels after trying rehabilitation.
An MRI taken Saturday revealed the partial tear of the UCL.
Lugo, 27, last pitched March 27, allowing four runs and eight hits in 4 1/3 innings during an exhibition game against the Washington Nationals. He was 2-1 with a 5.56 ERA in three spring training starts and one relief appearance.
He also pitched for Puerto Rico in the World Baseball Classic last month, going 2-1 with a 4.20 ERA in three starts covering a team-high 15 innings. After solid outings against Venezuela and the United States, he took the loss in the championship game won 8-0 by Team USA.
Lugo made his big league debut last July 1 and went 5-2 with a 2.67 ERA in eight starts and nine relief appearances. He was a big help down the stretch to an injury-depleted pitching staff, helping the Mets reach the National League wild-card game. The team was expecting him to provide depth again this season as a potential bullpen arm and spot starter.
New York's talented rotation is having trouble staying healthy once more. Left-hander Steven Matz has a flexor tendon strain and will be sidelined until at least May. Right-hander Noah Syndergaard left Monday's opener with a blister on the middle finger of his pitching hand, and his next start will be pushed back a day.