"I know he won't talk about it, so I'll give my big guy a shot," Jefferson said after Game 4, via Ben Rohrbach of Yahoo Sports. "Deron Williams missed shootaround this morning, because he had like a little bug—just really lethargic, had no energy—and I think that's what 'Bron had."
James finished with just 11 points on 4-of-13 shooting in the 111-108 loss.
Jefferson reiterated that James was "lethargic" but also credited the Celtics for making tough shots in the win.
"I had a tough game, period," the four-time MVP told reporters after Game 3. "Me personally, I didn't have it."
Fortunately for the Cavaliers, James looked healthier in Game 4, finishing with 34 points, six assists and five rebounds. Kyrie Irving scored 42 points as the Cavs earned a 112-99 win, extending their series lead to 3-1.
Cleveland will now try to close out the Eastern Conference Finals in Game 5 in Boston on Thursday.