Mets general manager Sandy Alderson confirmed Friday that Steven Matz will miss at least three weeks with a partial tear of his left lat muscle, but said the lefthander could be out longer.
"No one has guaranteed to us that it will be healed in three weeks," Alderson said during a news conference at Citi Field.
Alderson said Matz, a Ward Meville product and Stony Brook native, noticed the discomfort after his first start against Cincinnati on June 28 and was subsequently monitored by doctors, who determined that he could pitch in Los Angeles last Sunday.
After the start against the Dodgers, Alderson said it was decided that Matz would skip his next start, scheduled for Sunday against Arizona at Citi Field and Jonathon Niese would pitch.