McHugh -- who made his debut on Aug. 23 in place of the injured Johan Santana -- retired 20 of the 22 Rockies that he faced, including 10 in a row to complete his afternoon. He struck out nine over seven scoreless innings, but settled for a no-decision after New York's bullpen surrendered the only run of the game in the eighth inning.
McHugh became just the third Mets pitcher to throw at least seven scoreless innings in his Major League debut, and the first since Masato Yoshii did so in 1998. His nine strikeouts were the second most in franchise history in a rookie debut, trailing only the 11 that teammate Matt Harvey fanned earlier this season.
"Every game at this level is important," McHugh said after the start.
He was optioned back to Triple-A Buffalo the next day to clear a roster spot for Jeremy Hefner's return from paternity leave, but it was understood that he would rejoin the team as a September callup.
"This is my debut, but I hope to have a lot more," McHugh said. "But every game up here [is tough], and it's going to be a battle."
Joe Kelly gets the start for the Cardinals after he was reinserted back into the rotation on Wednesday.
Kelly hadn't started since Aug. 14, but he made two extended relief appearances, including 5 2/3 innings in the Cardinals' 19-inning, 6-3 loss to the Pirates on Aug. 19.
But his return on Wednesday didn't go well. Kelly allowed five runs over as many innings against the Pirates, allowing eight hits and walking three.
Mets: Club could return to five-man rotation briefly
When Matt Harvey's season ultimately comes to an end sometime in the next few weeks, New York will -- at least temporarily -- return to a five-man rotation.
Mets manager Terry Collins said that once the team shuts down Harvey for the season, the team will work with a five-man rotation until its final off-day before adding a sixth arm back into the mix. The Mets close out the season with 13 games in 13 days.
"When Harvey's done, you're talking about the September callup guys are possible guys to slip into that same spot," Collins said. "We probably can get by with five [starters] until the last off-day [Sept. 20]."
At 152 1/3 combined innings between the Majors and Triple-A, Harvey has roughly 15-20 innings left before he reaches his 165-170 innings limit set by general manager Sandy Alderson. He logged 135 2/3 innings last season in the Minors -- the reason the limit was set this year.
Cardinals: Wainwright's workload not a concern
Adam Wainwright is making the same return from the same surgery as the Nationals' Stephen Strasburg, but Wainwright's workload, at least according to the Cardinals, isn't a cause for concern.
"I don't know what the information is that [Washington is] getting from their medical people," Cardinals manager Mike Matheny said. "That's really what we go on. I don't pretend to be an expert in that field. We've been given the 'all progress forward' and 'full steam ahead' with Adam until we see anything out of the normal."
Wainwright has already thrown 168 2/3 innings through 27 starts after missing the 2011 season while he recovered from Tommy John surgery. If the Cardinals don't make any tweaks with their rotation, Wainwright would have six more starts this season, and could potentially make more in the postseason.