Stop Chris Judd.
Judd, returning after missing the final three rounds of the regular season due to a knee injury, inspired the Blues' third-quarter fightback and ultimately their passage to the second week of September.
"He was sensational ... there were a few others obviously (that lifted the team in the third term), but he was the one that stood out - in the centre-bounce clearances in particular," Longmire said ahead of Saturday night's semi-final between the two sides at ANZ Stadium.
"It's not as if he only does it once or twice, he's got a history of doing it and doing it in big games. That's why he's a superstar."
Longmire says it's too early in the week to decide who would be given first crack at Judd, but forecast a handful of his midfielders would spend time on the dual Brownlow medallist.
"They are the hardest ones to try and nullify, the players who go at the ball like that and are so good at the 50-50 moments," he said.
"But we think we've got a few blokes that are pretty good in that area as well, whether it's Josh Kennedy, Ryan O'Keefe or Luke Parker.
"I'm sure that group, maybe a couple of others, they'll all get a go at him at different times.
"But it's about us getting our hands on it. That's the best way to try and stop him."