We'll never know about Manu, because he spent his career coming off the bench. But on any given night, he could be just about as good as anyone I've seen.
One argument in his favor - at the end of games, he was on the floor against the best that other teams had to offer. And he kicked a lot of ass, on both ends of the floor. (People forget what a tough, tricky defender he was in his prime. Still pretty crafty.)
Would I put him on the list of Top 10 all time? Probably not, because of the role he played. Could he have earned his way onto it? Maybe. But I know this. If the criteria includes being a winner, then his rating goes way up.