I'm not arguing he didn't play well. I'm arguing that the reason he played well was because he was defended by one of the worst defensive PGs in the league against a team that, although solid overall defensively, had major trouble stopping quick PGs. Going into that series, we knew Duncan in the low post (with Sideshow and Big Z down there) would meet some resistance and that Manu might have a tough series since he would be guarded by Lebron/Pavolic/Snow, all decent defenders at the time. So the matchup to exploit was Parker vs. Boobie/Damon Jones (another terrible defender).
Besides that, the Cavs were so completely overmatched, it's not like Parker "willed" the team to victory in a hard fought series. The Spurs win that series with Derek Fisher at PG. It'd probably take them 6 games, but they win it nonetheless.