Buchholz scratched from start because of right arm tightness
Matt Koch started in his place.
Buchholz, who signed a minor league deal with Arizona on May 4, is 7-2 with a 2.01 ERA. He is 5-1 with a 1.66 ERA in nine starts since returning from the disabled list on July 24.
Koch made his 12th start of the season, but left after allowing four runs and eight hits in three innings.