The way he's started this season reminds me of Rooney towards the end. He might have a burst of pace to get into positions, but the fatigue shows itself in the touches after he's got the ball. Underhit/misdirected passes, tame/wayward shots, easily dispossessed, easily brushed off the ball, easily tripped over.
It's still early in the season and considering he didn't have a pre-season, there's still a chance that he'll get up to speed. He also has more weapons in his arsenal than Rooney, so he can still be effective as an aerial target and poacher. But for him not to be finished as a PL player, I think he has to readjust his game again.