Tuesday Matchup: D-backs (Gallen) vs. Rockies (Gray), Coors Field, 6:40 .m.

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Jon Gray is looking to get back on track in Tuesday's start against the Diamondbacks. The Rockies' right-hander has one win in seven starts since July 1. He has worked at least six innings in only two of those seven games. The one win? Against the Dodgers at Coors Field on July 29 when he allowed one run on three hits and three walks in eight innings. Zac Gallen will be making his second start for Arizona since being acquired July 31 from the Miami Marlins for infield prospect Jazz Chisolm. He won his D-backs debut six days ago against Philiadelphia, allowing one run in five innings.

Gray has his challenges on the D-backs, led by David Peralta (.478) and Ketel Marte (.444), the current D-backs roster has a composite .311 batting average against Gray. Gallen is that unknown for the Rockies.