FITNESS will be a large focus for Melbourne as it looks ahead to 2015, with coach Paul Roos telling his players to expect the toughest pre-season of their life.

No sooner had the Demons' 2014 campaign finished up with a 30-point loss to North Melbourne, than Roos had the players already turning their attention to next season.

It has been a disappointing season again for the Demons, who at times showed real promise with wins over top eight sides Richmond and Essendon, as well as downing the Crows at Adelaide Oval.

But Melbourne's best form was short lived, and the club finished the season on just four wins, having lost the last 10 games of the season.

An exhausted Tom McDonald said a lack of fitness was a key reason behind the Demons' disappointing finish to the season.

"Part of it is fitness," the key defender told AFL.com.au.

"That's why Roosy says to get ready for a big pre-season because we've been run over the top at the end of the year. Fitness has a lot to do with that, so I think that's an issue.

"The season has been a real disappointment I think. If we had continued on with the form from rounds 11 to 14 I think it would have been a success, but now we're back where we started really. We've maybe made a few little improvements in some areas but we really let ourselves down in the last five weeks."

In his fourth season, the 21-year-old has grown significantly as a key defender, playing every game but one.

With teammate James Frawley thrown into attack for most of the season, McDonald has had to face off against some of the competition's best key forwards, such as Lance Franklin, Nick Riewoldt and Jarryd Roughead, and has held his own.

But the youngster said he is keen to improve his game, and will look to work on his speed and power in the off-season to become a more dynamic defender.

"I've had the opportunity to play on some of the main key forwards so that's been really good to grow and learn," McDonald said.

"I probably haven't been as consistent as I'd like. When the team was going well I was doing a lot of good things but then dropped off in the last few weeks as well, which is disappointing.

"It has been a good year experience wise for me, and hopefully I can take that into next year and carry it through consistently.

"In the off-season it's hard to do a lot of team relating things, but I want to focus on leg strength, repeat speed and power.

"I've always been a naturally good distance runner, but I want to work on my speed and power so I can compete in the contest with those big forwards every week, so that's going to be a big emphasis."