Dahl, who was selected for his first MLB All-Star Game last month, was carted off the field.
Ian Desmond entered the Rockies' lineup in his place.
Dahl entered the night with a .302/.353/.526 slash line and 15 home runs in 99 appearances. His .879 OPS ranked 17th in the National League.
The 25-year-old Alabama native's rise into an everyday player for Colorado had been delayed on several occasions because of injuries.
"I've been hurt a lot early in my career, and a lot of crazy things have happened," Dahl told reporters in early July. "But I've persevered through them, and it just makes you realize how much you love playing."
Desmond, who'd been starting in left field as of late, is likely being shifted back to center for as long as Dahl is sidelined. Garrett Hampson and Raimel Tapia are probably going to split the extra playing time.