Arizona owns the worst record in baseball at 50-109. The Diamondbacks have lost 10 of their last 12 home games.
So anytime I can lay a short price against them, especially with the superior starting pitcher, I'm going to look to do that. 

Veteran Jon Gray goes for Colorado. Gray has failed to live up to No. 1 starter status with Colorado, but he's decent given that he has a 4.28 ERA and plays half of his games at Coors Field. 

Rookie Humberto Castellanos also has a 4.28 ERA. He has made only six big league starts. The Rockies have lost 24 fewer games than the Diamondbacks. 

Arizona is 6-24 in its last 30 games. Colorado is on a two-game win streak. The Rockies are 26-10 the past 36 times when favored.