The New York Mets are preparing to defend their National League championship without talented left-hander Steven Matz, who now appears to be a long shot to pitch in October after undergoing another checkup on his ailing shoulder, manager Terry Collins said Monday.

Matz was scratched Friday because of renewed soreness, and hasn't pitched since Aug. 14. There had been some hope that Matz could return as a reliever late this month or early October, but Collins told reporters Monday that even that scenario had become increasingly unlikely.

It's unclear what, if anything, prompted the Mets to further stall Matz's timetable.

The 25-year-old lefty is one of several key pitchers currently sidelined for the Mets, a list that includes Jacob deGrom, Matt Harvey, and Zack Wheeler. Prior to suffering the shoulder impingement that's limited him to just 22 starts this season, Matz posted a 3.40 ERA, 1.21 WHIP, and 129 strikeouts over 132 1/3 innings.

The news comes amid a late playoff push for the Mets, who entered Monday's game against the Marlins with a one-game lead over the San Francisco Giants for the NL's top wild-card spot.