The soreness was a result of Nunez's awkward stumble over first base when he reached on a fielder's choice in the second inning.
"On that ground ball up the middle, kind of like, he didn't know what to do, either to go head first or standing up. His cleat got caught and he wasn't feeling great," Red Sox manager Alex Cora said. "Before that at-bat, he's like, 'Let me see how it feels here.' I probably should have just taken it out of his hands there, but he was moving OK.
"Puts a good swing on [the double] and when I saw it I was like, 'You know what? We're going to take him out.' He'll be day to day over the weekend. He's not going to play tomorrow, and we'll see how he feels on Saturday."
It was almost exactly a year ago when Nunez sustained a PCL sprain in his right knee and reinjured it twice while trying to make comebacks, including Game 1 of the American League Division Series against the Astros, after which he was taken off the roster.
Due to that 2017 injury, Nunez has been less than 100 percent for most of this season, but he had finally been feeling like himself of late.
Cora, however, is confident that this injury is just of the nagging variety.
"Honestly, talking to [head athletic trainer Brad Pearson], we don't feel it's something serious," Cora said. "It's just, he felt it shifted a little bit, I guess, but he should be fine. He was running well on that ball off the wall. So like I said, we'll see how it goes over the weekend."