Smith homered off Cubs starter Ryan Dempster in the first inning, and he doubled and scored in the fourth before being replaced by Ryan Spilborghs.
Smith said he felt the tightness while running out the double.
"I just tweaked it or something, but it should be fine in a day or two," Smith said.
The two hits Sunday gave Smith 10 extra-base hits this season. He entered Sunday's play tied for fourth in the National League in that category. Smith is hitting .313 with two home runs and eight RBIs in 12 games.