The manager told the Shields Gazette: "He's worked so hard, but he gets tired, although that's normal. In the last few days, we've reduced intensity and made the sessions more technical and tactical.
"He's OK. But it's obvious for him that it will take him another two or three weeks to see him fully fit. In the last two weeks, he's been full time, a real full-time player in training with high intensity.
"But even if he can give us 100% for 45 minutes, or 80% for 65 minutes, it could be crucial."
Sunderland host Arsenal this afternoon.