I don't know why Manu Fan has to continuously point out "See, look how important Manu is!" as if the vast majority of Spurs fans don't realize how important a healthy Manu is to the Spurs. Obviously the Spurs would be much better off with Manu. You take away any individual out of the Big Three and the Spurs would either be in this hole or would have been swept.
With the Big Three intact, the Spurs would probably beat Dallas. But not for sure. If Pop had Vaughn as the backup point guard, Bowen and Hill at the end of the bench and Mason buried behind Finley, the Spurs would likely still lose to the Mavs. Even with Manu, the Mavs are a horrible matchup and Pop would likely be riding the wrong horses into the playoffs.