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CHICAGO -- When the Cardinals traded for Jordan Montgomery just prior to the MLB Trade Deadline, they knew of his vast potential as a 6-foot-6 left-handed starter with multiple plus-rated pitches and all the metrics that played into his moderate success with the Yankees.

What they didn’t know, however, was about his gritty makeup, and how he has always been driven by two older brothers who also double as his best friends.

The Cardinals were briefly tempted to try and work out a deal for superstar outfielder Juan Soto at the Deadline, but they backed away when they found out the personnel hits they would have to take, namely the top prospect in their farm system (6-foot-5, 250-pound slugger Jordan Walker) and top young talents at the MLB level (Dylan Carlson and Nolan Gorman). Instead, they shifted their focus to their greatest area of need after Jack Flaherty and Steven Matz continued to be hampered by injuries: Reliable starting pitching.

Landing 11-year MLB veteran José Quintana the day before the Deadline made the Cardinals better, but the move by president of baseball operations John Mozeliak and GM Michael Girsch to shockingly swipe Montgomery away from the Yankees was a needle-moving deal that might make St. Louis a serious contender again.

All Montgomery has done since becoming a Cardinal is go 4-0 while allowing just one earned run in 25 2/3 innings. Even more impressive is the fact that he’s struck out 24 batters compared to just three walks. The finest outing of his MLB career came earlier this week, when he threw a one-hit shutout against the Cubs. That performance -- the first complete game of his career -- put him in some rarified air, and his brother, Jay, was the first to congratulate him.

“I’ve got a text message from him waiting right now where he said, 'A Maddux' exclamation point,” said Montgomery of the performance, one in which he threw a shutout while needing fewer than 100 pitches. (Hall of Famer Greg Maddux, for whom the distinction is named for, had 13 such outings).

Such success from Montgomery has to be shocking to those in the Yankees organization after he didn’t register a win in his final eight starts in pinstripes. The difference with the birds on the bat as opposed to the pinstripes: Montgomery is throwing his fastball 30 percent of the time, as opposed to just 8.5 percent of the time as a Yankee.

“He’s been on a mission,” Cardinals manager Oliver Marmol said.

Montgomery, 29, was rocked emotionally by the trade, and he’s been reluctant to talk about his feelings about being dealt by the franchise he was drafted by and spent eight years in. His drive to be great, he said, has less to do with any grudge toward the Yankees and more the way he got started in baseball while playing with brothers, Jay, 34, and Josh, 30, back in Sumter, S.C.

“Growing up with two older brothers and playing above my age limit my whole life,” Montgomery said when asked about the source of his drive as an athlete. “Getting bullied by my two brothers, making me cry and go inside. My brother would hit me ground balls as hard as he could, and I wasn’t allowed to come off the field until I caught them all.

“That’s just how it was, growing up, and now they are my best friends. It’s great to have them as my two best friends.”

While some have expressed surprise that Montgomery has been as dominant as he has been so far, he bristles at the notion he is pitching above his talent level. His answer to such claims offers more insight into just how driven he is to perform at a high level after being traded from the Yankees to the Cardinals.

“I still don’t understand what the narrative is about me. I’ve been a good pitcher my whole career,” he said. “I expect a lot out of myself, I think my stuff plays no matter how many times they’ve seen me, and you can always count on me competing.”