Kilian went five innings in his major league debut, giving up three runs on three hits against the Cardinals, who won the game 7-4 in 10 innings. He walked two and struck out six.
"Best day of my life,'' Kilian said. "To be able to debut at Wrigley, Saturday night against the Cardinals and it starts raining, tied game in the ninth, I couldn't ask for anything better.''
Kilian was 2-0 with a 2.06 ERA in nine starts for Triple-A Iowa this season. He had 41 strikeouts in 39⅓ innings before being called up.
Kilian was acquired with outfielder Alexander Canario on July 31 for Bryant as part of the Cubs' roster tear-down. He has a career 2.08 ERA in three minor league seasons after being drafted in the eighth round by the Giants in 2019.
To make room on the 40-man roster, the Cubs DFA'd pitcher Conner Menez. They also recalled righty Anderson Espinoza to serve as the team's 27th man for the doubleheader. Kilian will be the team's eighth player to make his major league debut this season.