The free kick that led to Geelong midfielder Allen Christensen's match-winning goal over Carlton was "a bit strange" and not in the spirit of Friday night's thrilling contest, according to Blues coach Mick Malthouse.

Christensen received the decisive free kick at the 23-minute mark of the final quarter, when he led out for the ball and Blues defender Sam Docherty spoiled him.

The Cat received a free kick for a push in the back, but Docherty appeared to make minimal contact with Christensen.

Adding a further sense of confusion to the decision, play went on for several seconds before the non-controlling umpire, who was some distance from the contest, eventually paid the free. 

The Cats were one point down at the time, but Christensen coolly converted his chance from 40m to put the Cats five points up, and they were never headed from there.

WAS THIS A FREE KICK?

"(It was) a bit strange especially when the senior umpire was 20m away and I think he got it right," Malthouse said.

"I thought in the spirit of the game the way it was, it was probably play on, but then I would say that wouldn't I?"

The Blues' six-point to the Cats was eerily similar to their five-point loss in the teams' round 12 clash this year.

In that game, also played on a Friday night at Etihad Stadium, the Blues lost after forward Troy Menzel was denied what looked a certain free kick for high contact in the dying seconds.

Malthouse said both of those losses had been missed opportunities for his team.

"Perhaps certain things took place that, without going into it too deep, I thought we were probably a bit stiff to have lost both games," he said.

The Blues were hit hard by injury against the Cats, with David Ellard (foot), Dale Thomas (knee) and Menzel (shoulder) all unavailable in the last quarter of Friday night's game.

Malthouse said in his post-match press conference it was too early to know the extent of the trio's injuries.

Thomas hurt his left knee in the second quarter when Mathew Stokes fell across him. The former Magpie returned to the field, but Malthouse said he had subsequently copped a kick in the leg. 

Menzel suffered his injury in a third-quarter marking contest and did not take any further part in the game.

"I don't know whether it's an AC joint or whether it's been subluxed. All I know is he couldn't come back on so until you get medical clearance, it's a waste of time speculating, to be honest," Malthouse said.

Ellard took no further part in the game after a Geelong opponent fell across his leg when he was kicking out of the Blues' backline midway through the second quarter. 

Malthouse said Ellard had been sent to hospital to have X-rays on his foot.

The Blues coach praised the performance of Andrew Carrazzo on Joel Selwood.

Carrazzo struggled to contain Selwood in the first half as he racked up 17 possessions, but hit back in the second half, keeping the Geelong skipper to just four possessions.

"We were a bit disappointed in the first half with him," Malthouse said.

"But Andrew's got a massive amount of pride (and) for a bloke who's been in and out of the side because of injury, it's an extraordinary effort, really."