The stiffness was the direct result of a headfirst slide d'Arnaud made into third base in the fourth. d'Arnaud briefly consulted with manager Clint Hurdle and head trainer Brad Henderson after he was slow to get up, but he remained in the game and scored Pittsburgh's first run.
After playing one more inning in the field, though, d'Arnaud left the game.
"At first, when it happened, it was a little tight, but I thought it would be fine," he said afterward. "The next inning on defense, as the inning went on it kind of locked up more and more to the point where I felt like I was just hurting the team. I let the trainers know and they took action."
Despite being shaken up on the slide, d'Arnaud's aggressive decision to advance to third on a single by Neil Walker set the Pirates up to score twice in the fourth. Walker advanced to second on Jay Bruce's throw to third, which put d'Arnaud and Walker in position to come home on a groundout and subsequent sacrifice fly. Those ended up being the only two runs scored in the game.
d'Arnaud was warned by the trainers that the stiffness will likely be worse when he wakes up on Tuesday, which would suggest that he likely won't start the second game of a three-game set against the Reds.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.