X-rays were negative, and he's not expected to miss any time following Milwaukee's off-day on Thursday.
"I couldn't push off it or run, so I wasn't going to be of much use," Shaw said. "I'll be fine."
Shaw completed his first at-bat and struck out swinging against Reds right-hander Luis Castillo, then went into the clubhouse. He was replaced at third base by Hernan Perez in the bottom of the frame.
"He banged a ball off his foot, just a bruise," said Brewers manager Craig Counsell. "Off-day helps."
Shaw has appeared in 31 of the Brewers' 32 games this season, including 30 starts, and is leading the team in runs (19), doubles (8) and total bases (53). He snapped an 0-for-19 skid Tuesday night with a two-run homer in the Brewers' 7-6 win. He is batting .241 this season with six homers and 16 RBIs.
As for wearing a shin guard with the flap to protect the foot?
"It'll be on Friday," Shaw said.
Jeff Wallner is a contributor to MLB.com based in Cincinnati.