He's always had trouble with guys like Billups and Stuckey. Other than that though, he's not worse than average, and that's good enough for this team. Now Vince is a completely different matter where Leesus is going to be missed.
Both Nelson and Stuckey were volume scorers this last game. Between them, they took 33 FG attempts. That both players aggressively attacked the basket can explain, in part, a lack of defensive focus for either player.
Do not forget, whereas Nelson had 8 assists, Stuckey only had 3.
What was the effect on team performance? Stuckey was -7 and Nelson was +7 in the +/- stat box.