I said this in an earlier thread and think it still stands. Nate wasn't brought in to be part of the rotation. He was brought in to be a backup for Rondo in case Rondo got hurt.
I figured it would be more along the lines of Rondo missing a game or two - but clearly Rondo couldn't go for a large part of the game, and Nate got after it. His game isn't as suited to a pass first PG - he needs to jack up a few shots and make a few drives to get the defense responding to him and then create off that - which is what he did.
Nate got the lead last night, Paul Pierce held it.
BTW - Rondo was really hurting in the second half - I liked how they posted him at the top of the key to keep Jameer honest.