Coach Mark Harvey said Tarrant, who didn’t train on Wednesday night and is struggling with an achilles injury, was likely to join key defenders Antoni Grover (hamstring) and Luke McPharlin (knee) on the sidelines.
Riewoldt leads the Coleman Medal race with 53 goals and has benefited from improved inside-50 numbers in the Tigers’ past four wins, with Damien Hardwick’s side going into attack more than 50 times a game.
“We've looked at their supply over the past month,” Harvey said from Fremantle Oval on Thursday. “Their younger players are really starting to make the most of their opportunities and really establishing themselves in the team.
“And then on top of that they've got their big boy down there that's probably in the best form of any forward in the competition.
“(But) it's what you do before the ball comes down that's important… how much pressure you can put on up the field.”
Harvey said Fremantle had options to cover for its trio of injured key defenders, with Michael Johnson and Alex Silvagni in the side and All-Australian centre half-back Adam McPhee primed for a return to defence.
The coach said Fremantle had put a lot of time into preparing for the 195cm Riewoldt, who is listed as 2cm taller than cousin, St Kilda star Nick.
“He's got a different physique that probably suggests he's not as tall as Nick, but he actually plays tall,” Harvey said.
“He travels, he tries to work his opponent over (and) his timing is spot on at the moment. He's one grab and he's getting really good supply.
“I think as more time progresses with him and the more study that goes into him - and we've put a lot of study into him - the more you have to keep finding different avenues about the way you want to play football.
“We'd like to think we can continue on in that area but we understand we might have to support [our defence] a bit more.”
Harvey also confirmed Nat Fyfe (concussion) won’t play, with a host of young players in line for selection, including Nick Suban, Clancee Pearce, Tim Ruffles and Jesse Crichton, who is yet to debut.
Senior players Byron Schammer and Steven Dodd are also being considered to face the 15th-placed Tigers, with Michael Barlow’s leg injury prompting at least three forced changes.
Des Headland will play his first game back from a knee injury with WAFL side Subiaco and Harvey said the 29-year-old had stripped off 2kg in an effort to protect his knees in the latter stages of his career.
