ST. LOUIS -- Remarkably, the same Jordan Montgomery who failed to register a victory in his final eight starts with the Yankees suddenly can do no wrong with a Cardinals franchise delighted to have the 6-foot-6 lefty on their starting staff.

Montgomery, acquired in a deal with the Yanks prior to the Trade Deadline, finally gave up a run in a St. Louis uniform on Wednesday night, but even that was a weak, 79.4 mph grounder that found a hole only because the Cards were in a shift defense. 

After silencing the Rockies in a 5-1 win at Busch Stadium, Montgomery’s three-game stat line with the Cardinals is downright eye-popping, especially when considering the trouble that he had over a final six-week stretch with the Yankees.

In 16 2/3 innings as a Cardinal, Montgomery is 3-0 with an 0.54 ERA and a 0.90 WHIP. He’s surrendered just 12 hits and has 17 strikeouts compared to just three walks. That one run on an opposite-field bleeder by Charlie Blackmon that would have been a double-play ball had the Cardinals not been in a shift, ended Montgomery’s scoreless streak at 13 1/3 innings.

That’s tied for the fifth-best start to a Cardinal career by a hurler, equaling Alex Reyes (2016) and John Urrea (1977).

“It’s been great having him here pounding the zone and attacking teams,” marveled rookie second baseman Nolan Gorman, who had two hits and three RBIs on Wednesday to provide Montgomery all the run support he needed. “It’s been fun to watch, for sure.”

So, what, you might wonder, has changed for Montgomery? The 29-year-old didn’t win a game with the Yankees from June 17 to July 31 for a variety of reasons and he got saddled with six no-decisions and two losses. Starting with a June 22 road no-decision against Tampa Bay, when he surrendered multiple home runs for the first time all season, to a July 26 outing against the Mets, where he gave up four first-inning runs, followed by an ugly outing against Kansas City, where he failed to reach the fifth inning, his final stretch with the Yanks proved to be rocky one.

Montgomery flipped that script in St. Louis, holding the Yankees scoreless over five innings in his first outing with the Cards. Then, with the National League Central on the line, he blanked the rival Brewers over six innings while piling up eight strikeouts.

Against Colorado, Montgomery was surprisingly pulled after getting slugger C.J. Cron to ground into a double play. But he still befuddled the Rockies to the point that they struck out eight times.

Again, what’s changed for Montgomery from New York to St. Louis?

“Nothing,” Montgomery said. “I was tipping [pitches] in Queens [against the Mets], and [against Kansas City], I was one pitch away. Whatever … I’m a competitor and I’m trying to win every game. I want to be a guy this team can depend on.”

One thing that has changed for Montgomery is his willingness to challenge right-handed hitters inside with his fastball. His ability to spot that pitch has made his changeup even more effective and his big sweeping curveball even more baffling.

“If I’m locating it glove-side, it opens up my changeup down and away so they can’t just foul me off to death,” said Montgomery, who previously credited veteran catcher Yadier Molina with pressing him to throw his fastball more. “I’m just going to keep trying to execute with [the fastball].”

Cardinals manager Oliver Marmol got a glimpse of Montgomery’s fiery competitiveness when he didn’t want to come out of the game in the sixth inning at 87 pitches -- 60 for strikes.

“We’ve talked a lot about stabilizing that rotation and doing a good job of getting the right guys,” Marmol said of the Deadline haul of José Quintana and Montgomery -- moves that have helped them go 11-3 since Aug. 2.

“[Montgomery] is tougher than he may give off because he’s a mellow kid and kind of low key. But he’s ultra-competitive and loves being out there. Today, he definitely didn’t want to come out of that game, but he fits well with what we have going on here.”

Asked late Wednesday if any part of him wanted to send a message to the Yankees that they made a mistake in trading him, Montgomery chose his words carefully and decided to look forward to his future with the Cardinals instead of replaying what went wrong in pinstripes.

“Getting traded is part of the business,” Montgomery said. “I know what I’m worth and I think the Cardinals know what I’m worth.”