While the game marks DeJong's first in Busch Stadium, he noted he does have some experience in the venue.
"I was here before the Draft in '15," DeJong said. "It's a cathedral, and I can't wait to play here."
The Cardinals are impressed with DeJong's offensive ability, and they hope he can provide some power in the lineup.
In 46 outings with Triple-A Memphis this season, DeJong hit .294 with 11 home runs and nine doubles. He spent most of his time at shortstop, but he noted the challenge of playing at second base -- where he started Monday -- isn't new to him.
"Primarily in college, I was a second baseman," DeJong said. "I feel comfortable over there."
Playing in front of his parents and some friends, DeJong might be expected to have some nerves. But he said he'd do his best to focus in between the lines and tune everything else out. That message was echoed by fellow infielder Greg Garcia, who said he's seen DeJong as a poised young player before and didn't expect his first start to be anything different.
"He's a good player," Garcia said. "He's a really good player."
If anything, the highest expectations placed on the rookie came from one person, Cardinals general manager John Mozeliak. Asked in the Cards' dugout what he wants to see from DeJong, Mozeliak wasted little time setting a lofty standard.
"I'd be happy if he just did what he did yesterday," Mozeliak joked of the home run. "Four times. No pressure."
Outfielder Stephen Piscotty, who left the Cardinals before their series against Colorado to attend to a personal matter, could be back with the club soon. While Mozeliak said he didn't have additional information to share, he said he expected to see Piscotty back soon.
"Hopefully he'll be back with the club in the next day or so," Mozeliak said. "But not a whole lot to add on that."
Piscotty last played on May 25. The right fielder was hitting .224 with two home runs at the time he left the club.
Scott Chasen is a reporter for MLB.com based in Chicago and covered the Cardinals on Monday. This story was not subject to the approval of Major League Baseball or its clubs.