Johnson, who was available to pinch-hit, said he likely would have started on Sunday if it would have been a night game, but manager Brad Mills wanted to give him more time. Johnson began the day hitting .319 with eight homers and 42 RBIs.
"It's just a little soreness, but nothing serious," said Johnson, who took batting practice before the game.
Entering Sunday, Johnson ranked sixth in the National League in batting average (.333) since the All-Star break and ranked second among all NL rookies in batting average this season. He also ranked fourth in slugging percentage. The Astros are 40-30 in games in which he started at third base.
"I'm just going to keep going out there every day, try to help the team win and get better, and boost the stats a little bit," Johnson said.