MELBOURNE is searching for an answer to its fourth-quarter fadeouts, but the Demons can almost certainly scrub 'lack of fitness' from being a possible reason.

For the second consecutive week, Melbourne was held goalless in the final quarter and endured an anxiety-laden finish as its opponent reeled in a big deficit.

On Friday night, that resulted in a 15-point three-quarter time lead against Brisbane flipping into a five-point loss. Last week, a comfortable 33-point lead at the final change against North Melbourne turned into a nail-biting three-point victory when the Dees were held scoreless in the final term.

That's reflective of a long trend for Melbourne. Last year, the Demons were +8.7 points in final terms and ranked No.1 in the League for fourth quarter differential. Until round nine this year, they were +10.4 points in final quarters and again ranked No.1 in the League for fourth term differential to that point.

However, in the six games since round 10, Simon Goodwin's side is suddenly -14.2 points in final quarters. They have gone from first to worst, ranked dead-last throughout that stretch for last quarter differential.

It's led to some queries around Melbourne's fitness and the side's ability to run out games, but that's a theory that's quickly dispelled by the numbers.

On Friday night, the Telstra Tracker shows the Demons ran a total distance of 297km. It was the most covered by any side across the entire round, and 9km more than the Lions during the game.

The Telstra Tracker also shows Melbourne ran 43km at high speed, 6km more than Brisbane. It completed 272 total sprints, 50 more than Brisbane, and it ran 21 repeat sprints, four more than Brisbane.

The Demons' average speed in defence – a number closely tracked by clubs as it displays the side's work rate without the ball – was 8.3km p/h. It was significantly higher than the Lions at 7.4km p/h and the fifth best of any side across the round.

Those numbers came within a game where Melbourne had six more clearances than Brisbane, 24 more contested possession and 18 more tackles.

But they are also similar throughout Melbourne's six-week stretch of being the worst fourth-quarter side in the competition.

In fact, despite going 2-4 during that period and suffering significant losses to Fremantle and Collingwood worth 92 and 38 points respectively, Melbourne has covered more total distance than its opponents in four of its last six matches.

The Demons have also covered more distance at high speed than their opponents in four of those six matches, have completed more total sprints than their opponents in four of those six matches, and have had a higher average speed in defence than their opponents in half of those games.

So, if it's not fitness, what's behind the fourth quarter fadeouts? It's a question Goodwin will be desperately trying to solve in order to save Melbourne's season, but it could have something to do with the side's transition in age profile.

Over the weekend, the Demons had nine players aged 22 or younger in their side (Daniel Turner, Trent Rivers, Jacob van Rooyen, Taj Woewodin, Judd McVee, Andy Moniz-Wakefield, Caleb Windsor, Koltyn Tholstrup and Kynan Brown).

They had just 10 players who had played over 100 games, while they had nine players who had played under 50 matches. Brisbane, conversely, had far more experience with 16 of its 23 players having 100-plus games under their belt.

But does that add to Melbourne's conservatism late in games, rather than any perceived fitness issues? It's a theory Goodwin suggested speaking after Friday night's defeat at the Gabba.

"It was a range of things," Goodwin said.

"Definitely, their midfield got on top, certainly in transition. They were able to transition the ball way too easily from one end of the ground to the other. They had a lot of uncontested possessions.

"In reality, we probably went a little bit safe. It's a big occasion for our group and we've got a lot of young players playing at the moment. We probably went into our shells a little bit, we went a little bit safe with the ball, and that added to the momentum.

"There's a bit to unpack in that last quarter for us. We'll go away and have a look at that. But for three quarters, there's a lot to work with. It's probably the best we've played."