MELBOURNE coach Simon Goodwin believes it's not panic stations yet, but admitted his side are "not quite at their best" after falling to back-to-back defeats for the first time in almost two years.

The reigning premiers were unable to atone for their shock defeat to Fremantle a week prior at the MCG, falling to a fast-finishing Sydney outfit on their home deck by 12 points on Saturday evening.

Goodwin's charges led by as many as 26 points early in the second term and not even a Herculean performance from Max Gawn was enough to stifle the Swans' momentum, who booted nine goals to Melbourne's four after quarter-time.

When asked if the players had been going through the motions after winning their first 10 games, Goodwin was adamant the Demons hadn't become complacent and needed to find ways to improve.

"No not at all, it's just what AFL footy is like, it's very tough to win and you've got to keep executing at your best, and you've got to have your game in check the whole way through," Goodwin said post-game.

"No one just goes and hands you wins. You've got to go and earn them. The season will have momentum swings in it from a game-to-game perspective, and we're just not quite at our best at the moment. We've played two pretty good footy teams. 

"We're certainly not panicking by any stretch of the imagination, but we've got to continue our purpose. We've got to continue to find ways to get better. We've got to continue to forge ahead in our season but that's what AFL seasons are about. They're a marathon for a reason. 

"You don't go through undefeated, you have got to find ways to win all the time. And as a coaching group, as a playing group we'll go away, we'll assess it, we'll look at it and we'll find ways to get better."

Melbourne has been without key forward Tom McDonald throughout its lean patch with the veteran missing a second successive game after being withdrawn from the contest due to ankle soreness.

Goodwin said McDonald will have scans early in the week to determine the severity of the blow, while not ruling out a potential lisfranc injury.

"He obviously trained throughout the week and he's still a bit sore, so we've got to go away and ... look a bit deeper into that and find out the reasons why," Goodwin said.

"He will have some scans early in the week and we'll get a bit more information and be able to pass it on at that point.

"It's something we've got to look at with the foot. He's clearly still sore so we've got to dig a bit deeper."