Diamondbacks RHP Zac Gallen (7-10, 5.40) vs. Astros LHP Colton Gordon (3-2, 4.67).

At Chase Field: Gallen has allowed one earned run or fewer in two of his past three starts. Most recently, on July 12 in Anaheim, he gave up six earned runs in five innings to the Angels. Gallen has had moments of brilliance on the mound this season, but has not been consistent. He is 1-1 with a 3.16 earned run average over five career starts against the Astros. In his last start against them on Sept. 29, 2023, at Chase Field, Gallen lost 2-1, though he struck out seven in 6â…“ innings. … Gordon worked out of the bullpen in his last outing on July 13, but he’s been in the starting rotation since the middle of May. His longest start of the season has lasted six innings, and he gave up a season-high five earned runs to the Cleveland Guardians in his last start on July 7. Gordon has allowed 10 home runs in 10 starts this season.

Coming up

July 22: At Chase Field, 6:40 p.m., Diamondbacks LHP Eduardo Rodriguez (3-6, 5.94) vs. Astros LHP Framber Valdez (10-4, 2.75).

July 23: At Chase Field, 12:40 p.m., Diamondbacks RHP Brandon Pfaadt (10-6, 4.82) vs. Astros LHP Brandon Walter (1-3, 3.66).

July 24: Off.

July 25: At Pittsburgh, 3:40 p.m., Diamondbacks RHP Ryne Nelson (6-2, 3.52) vs. Pirates TBA.