Davydenko is the highest level Nadal has ever faced. Federer is the highest level Hewitt has ever faced. As you guys always say, "its a matchup thing"....
The Hewitt-Federer rivalry proves this, because when Federer was serve-volleying, Hewitt was beating him. As soon as Federer switched to predominantly baseline tennis, every match was dominated by Federer from that point on.