Fremantle could be without its two best small forwards for round one, after Hayden Ballantyne injured his calf and Michael Walters was reported during Sunday’s NAB Challenge clash against the Sydney Swans.

On a difficult day for football with strong winds and late rain, Ballantyne finished up with calf soreness that could signal a spell on the sidelines if a strain is diagnosed.

Walters was reported for misconduct in a third quarter incident when he ran into Craig Bird while the Swan’s head was over the ball.

Watch the incident between Walters and Bird

Freo senior coach Ross Lyon didn't see the Walters collision but conceded Ballantyne's chances of facing Port Adelaide on April 5 were in jeopardy.

Ross Lyon Q & A - NAB Challenge v Sydney

"We've got a couple of little concerns," Lyon said.

"(Tendai) Mzungu tightened up in the hamstring so I think he'll be OK, but Ballantyne looks like he’s hurt a calf so that's a concern.

"If it is, he’ll probably miss round one, so that's not ideal."

Mzungu was subbed off for Lachie Weller in the second half and David Mundy also tightened up late in what was a physical game.

But Nat Fyfe returned successfully from a hamstring injury and was one of the team's better players.

Nat Fyfe flies and kicks Freo's first

Lyon said fatigue wasn't the reason behind Ballantyne's injury.

"They're relatively fresh because under the CBA you get two three-day breaks, so they've had two consecutive weeks of three-day weekends," he said.

"It's not like they've been in at the club a lot.

"Maybe it's been ‘unders’ a little bit … everyone's going to get a soft tissue, you hope not to get them but it's part of the game and you try and get through unscathed but it doesn't always work that way."

Ruckman Aaron Sandilands didn't make the trip despite being named in the expanded squad but should play against West Coast next Sunday in their final NAB Challenge game.

"He tightened up … he's a unique frame so we're expectant he'll play against West Coast," Lyon said.

Lyon was pleased with the performance of Lachie Neale, who racked up 33 touches as the Dockers' best midfielder, but said Hayden Crozier and Tom Sheridan "could have done more" to press their cases for round one.