Woodruff was warming up to pitch the bottom of the fifth when catcher Omar Nárvaez summoned the team's training staff to the mound. After a brief meeting with the trainers and manager Craig Counsell, Woodruff departed.
Woodruff had allowed two runs in four innings. He entered the game at 5-2 with a 4.76 ERA in eight starts.
"He had some pain in his ankle on each pitch,'' Brewers manager Craig Counsell said following Milwaukee's 4-2 loss. "I'm not ruling him out for his next start. He obviously was throwing the ball really well, but there was significant pain in each pitch.''
On Monday, Milwaukee placed right-hander Freddy Peralta on the injured list with a right shoulder strain that is expected to keep him out for a significant period.
The Associated Press contributed to this report.