Seth Lugo, who has a 2.65 ERA in nine relief appearances this season, will start in Matz's absence.
"He felt great after his start [Sunday]," said Collins. "The following day, he threw a curveball and felt some discomfort in his shoulder. Did not feel it while throwing a fastball. The next day he got on the mound, threw some fastballs, and when he wanted to throw a curveball, his shoulder bugged him again. As a precaution, we got to skip him this time."
Matz is not quite sure what caused it, and he initially hoped that the discomfort would gradually disappear. But, he said it didn't heal the way he wanted it to.
"It's just discomfort, I'm really not worried about it," said Matz.
Matz, 25, has been pitching with a bone spur in his elbow that will require surgery after the season. Collins doesn't believe this current issue was influenced by the problems Matz has faced with his elbow, though. In addition, Matz stated that his arm had been feeling great up to his last start versus San Diego, an outing in which he took a no-hitter into the eighth inning.
"My elbow was feeling good," said Matz. "This may set me back a little bit routine-wise, hopefully it's just skipping a start and I'll be back to where I was."
That's the hope at least. Matz and Collins said that they weren't sure what the plan would be regarding the left-hander's shoulder. As of now, the club is taking his setback day by day.
"You got to do what's right, and what's right is to make sure that down the road this kid is going to be healthy," said Collins. "The shoulder is something you do not want to mess with."
Justin Wise is a reporter for MLB.com based in the Bay Area and covered the Mets on Thursday. This story was not subject to the approval of Major League Baseball or its clubs.