He's not slower in any sort of way that matters. The issue is when he's trying to burst off from a fully stopped position which almost never works with any regularity for any footballer ever. If he's receiving the ball when our play is ridiculously slow and static, and then kind of loitering to size up the defender, there's just a very low probability that he can skin him 1v1. Messi is best when he's receiving the ball while he's moving and on his toes. The defender is either backing off or committing, which allows Messi to exploit any positioning or balance weaknesses and slide past him with ease because the defender can't react quickly enough to shift his balance and stop Messi from passing. If Messi's flat footed and the defender is fully ready to turn in either direction to stop him, wtf is he supposed to do?
It's a problem when Barca plays slow, cautious games or when Messi himself decides he wants to play in third gear completely. An active and mobile Messi is the best dribbler the game has ever seen.
Just watch how almost every one of 10/11 Messi's best 1v1 or more dribbles come when he's running at them from the onset. His advantages in acceleration, balance, technique, control, etc. only come out in motion, otherwise there's little he can do unless someone blindly charges at him like a dumb brute (looking at you Milner).
