He had two third down receptions on their first touchdown drive to set up the 1 yard touchdown run by The Freezer. He had another third down reception on their next touchdown drive. Right after Blount had his huge touchdown run, the first pass was to Nelson and it got them out of bad field position. After the first onside kick failed, he caught a 5 yard touchdown reception. Those were all big plays, but this one was the biggest. From the play-by-play at NFL.com:
(3:01) (Shotgun) 12-A.Rodgers pass deep left to 87-J.Nelson for 40 yards, TOUCHDOWN [95-A.Haynesworth].
With 4:25 remaining, the Buccaneers had just scored to get within 2 points and then failed on another onside kick attempt. If the Packers were stopped at the 40 yard line on third down, they might have punted. A failed 4th down attempt would have given the Bucs great field position when they only needed a field goal. Instead of worrying about that decision, Nelson ran by his man in coverage and scored the touchdown to give them a two score lead with 3 minutes to go.