An MRI revealed inflammation in deGrom's right lat. He'll refrain from throwing for a few days.
Right-handed reliever Miguel Castro is starting in his place against the St. Louis Cardinals.
The injury isn't believed to be serious, a source told Jeff Passan of ESPN. DeGrom reportedly isn't expected to miss more than one start.
The 32-year-old has been cruising to start the 2021 season. He's 2-2 with a microscopic 0.51 ERA and 0.57 WHIP with 59 strikeouts across 35 innings.