Marwin Gonzalez led off the Astros' fourth and singled on a ball back through the middle that struck the rookie on his left leg.
Once the dust had settled from the play that saw Gonzalez reach second on a throwing error by catcher Bobby Wilson, Rays manager Kevin Cash went to the mound accompanied by assistant athletic trainer Paul Harker.
Snell tested his foot, throwing several pitches before a brief conference that resulted in him leaving the game.
Snell said Harker asked him if he felt normal, and the rookie told him, "Not normal, but I can go." Snell said Harker then told him they didn't want to "risk anything."
Danny Farquhar came in to replace Snell with the Astros leading, 4-0. Farquhar allowed an RBI single to Alex Bregman -- a run charged to Snell -- to make it 5-0. Farquhar finished with four strikeouts over two innings.