"It's a slight pull, we'll see how it is [Thursday]," Williams said. "I don't need an MRI."
Williams first felt something in his groin while pitching to Blue Jays slugger Edwin Encarnacion, but he thought he could fight through it. The very next pitch Williams threw, however, a 1-2 offering to Encarnacion, is when he knew he could no longer continue pitching.
Williams, who relieved starter Lucas Harrell in the fifth, immediately grimaced after the pitch and signaled toward the Astros' dugout, prompting manager Bo Porter and trainer Rex Jones to come out to the mound to check on the reliever.
Following a brief meeting, Williams walked off the field and was replaced by righty Josh Zeid, who was recalled from Triple-A Oklahoma City on Tuesday.
"After he gets home tonight, and goes to sleep and comes back [Thursday], the trainers will be able to better assess it," Porter said.
Williams threw 1 1/3 scoreless innings, while walking two and striking out one.