Melbourne young gun Christian Petracca has hit career-best fitness levels as he eyes further time in the midfield in 2018.

The former no. 2 draft pick has shaved 10 seconds off his personal best time trial and has spent the pre-season training with the midfield group, working on his endurance and stoppage work.

The 22-year-old will remain in the forward line for large chunks of games, but is confident his newfound fitness will allow him to spend stages in the engine room.

"I have improved my running a lot," Petracca told AFL.com.au.

"That was my biggest focus throughout the off-season and pre-season.

"I'm always going to have that as something I need to improve on and so far I have knocked a lot off my time, and I'm looking for more."

After struggling to maintain his teammates pace in running drills early in his career, Petracca is experiencing no such issues in 2018, emerging as a real leader.

"I could always compete in games and sessions but it's more about getting from contest to contest at a good pace and not getting there and being stuffed," Petracca said.

"Now I'm getting there and being quite fresh and feeling good."

Petracca averaged 18.8 disposals and kicked 26 goals in 2017, and is entering his fourth year in the AFL.