Marquis Daniels is sick.

Not sniffly nose sick, but that stay-in-bed-all-day kind of sick where you can’t help but feel bad for him when you see that pained look on his face.

Daniels has been battling the flu the entire week, but he still played on Thursday night against the Cavaliers. He started, in fact, in place of Paul Pierce.

He fought through picks, defenders, and illness. Daniels hustled for 31 minutes, defended LeBron James, grabbed three rebounds, and picked off a steal along the way.

“He did a great job,” said Glen Davis. “Being sick is tough. He’s a competitor and he plays hard. But he went out there and did what he had to do.”

After the game Daniels looked exhausted as he slouched at his locker. His voice was faint and he  simply shook his head when asked how he felt.

The Celtics will not practice on Friday. Daniels will wait until then to talk to the doctors about what he kind of activity he should or should not do.

But even though he is sick, it’s his dedication that’s most contagious.

“I commend him because the last day or so he’s been somewhat shaky and not strong,“ said Ray Allen. “You could tell that his energy was very low. So for him to be out there, I definitely commend him.”