Rookie Corbin Carroll accounted for the game’s only run with a two-out RBI single in the eighth inning against Mark Leiter Jr. Seiya Suzuki nearly made a terrific catch in right field, but the ball hit the grass in front of his glove and the out call was overturned by a replay review.
"That’s a good team. We ran into a tough situation today," Cubs starter Jameson Taillon said. "September baseball is meant to be close games and every inch matters."
Arizona (74-68) won for the fourth time in five games overall. It moved within two games of Chicago for the No. 2 spot in the NL wild-card standings.
Gallen (15-7) struck out nine and walked one after he dropped his previous two outings. Making his 111th career start, he got a celebratory dousing from Carroll and other teammates as he left the field.
"I’ve been grinding the last couple of weeks," Gallen said. "This a team we’re tracking behind. I’m just trying to go out there and do my job and put a stamp on it."
CHICAGO, ILLINOIS - SEPTEMBER 08: Zac Gallen #23 of the Arizona Diamondbacks delivers a pitch against the Chicago Cubs during the ninth inning at Wrigley Field on September 08, 2023 in Chicago, Illinois. (Photo by Michael Reaves/Getty Images)
Pitching coach Brent Strom said the Friday’s damp, mid-60s weather played a part.
"The environment helped," he said on a day neither team had much success reaching the warning track. "This was a great pitchers’ day today. He was able to challenge people and force the issue."
It was Gallen’s first complete game since he threw a one-hitter in a 5-0 victory over Atlanta in a seven-inning doubleheader opener on April 25, 2021; Madison Bumgarner then threw a seven-inning no-hitter in the second game.
Gallen’s complete game was the 30th in the major leagues this season, six shy of last year’s total.
Chicago wasted a strong start by Jameson Taillon, who struck out nine while pitching six innings of one-hit ball. Suzuki had two hits for the Cubs (76-66).
José Cuas (3-1) surrendered Lourdes Gurriel Jr.'s leadoff single in the eighth. He walked Gabriel Moreno and struck out Jordan Lawlar before he was replaced by Leiter.
Gallen retired his first 10 batters before he hit Nico Hoerner with one out in the fourth. Suzuki singled with one out in the fifth for Chicago’s first hit.
Carroll singled with two out in the sixth for Arizona’s first hit. Carroll then swiped second and advanced to third on a throwing error on catcher Miguel Amaya, but Ketel Marte bounced to first for the final out of the inning.
Carroll drew a walk to start the game, then stole second and went to third on a throwing error. But Taillon escaped the jam by striking out the next three Diamondbacks.
Cubs: RHP Brad Boxberger (forearm strain) was activated from the 60-day injured list, and RHP Keegan Thompson was optioned to Triple-A Iowa.
Arizona RHP Merrill Kelly (11-6, 3.22 ERA) faces LHP Justin Steele (16-3, 2.55 ERA) on Saturday afternoon.