Former Collingwood ruck-forward Mason Cox is yet to debut for Fremantle after being handed a career lifeline but is no guarantee to face West Coast next Sunday.
Jackson has often played better solo and was the dominant force on the ground in Friday night's 7.3 (45) to 5.9 (39) win at Adelaide Oval, where the Dockers claimed their fourth victory on the spin.
Jackson recorded 38 hitouts, 17 disposals, nine tackles, five clearances and five marks as he outpointed Collingwood's Darcy Cameron and Oscar Steene.
"He was super and got us going early in the third," Longmuir said.
"We struggled with field position, I thought our pressure was horrible in the first half - he helped us get on top in those areas in the third quarter.
".... His aerial in particular in the second half is really strong. He marked it like it was a dry weather night.
"He was instrumental in helping to spin the game."
Longmuir was disappointed for Darcy, who has had a frustrating run with injury and was concussed after he went head-first into Collingwood's Ned Long in the second quarter.
"It's an unlucky incident. It's going to cost him a little bit of time," Longmuir said.
" I feel feel bad for him, but we want to make sure we look after him as well. So he'll enter the protocols, clearly.
"We had a focus of trying to build his game time tonight as well. So he'll be right, he'll bounce back and we'll get him back in the team."
Longmuir didn't want to buy into whether he'd deploy two rucks against West Coast.
"I'm trying to enjoy the win, mate," Longmuir joked.
"We'll see. Haven't really dove into West Coast.
"I think they're only playing one ruck but they've got some real height across their team so we'll work out that as it comes."
