COMPLACENCY was behind Melbourne's poor finish under Paul Roos' coaching, Christian Petracca says.

The Demons were on 10 wins with two rounds remaining and a finals spot loomed had they won both matches.

Instead, Melbourne barely fired a shot.

It fell to a Carlton side that was on a nine-match losing streak before being smashed against Geelong by 111 points in Roos' final game as coach.

For Petracca, it was a sour end to the year.

"We got a bit complacent against Carlton and thought, we've won three on the trot and everything's working well, this week it will come easy to us," Petracca told AFL.com.au.

"The week against Geelong was a bit more bitter.

"To send Roosy off like that was disappointing and we were all pretty upset, but you learn from your mistakes."

Simon Goodwin will take over from Roos after the former Adelaide champion spent the last two years as a senior assistant at the Demons.

Petracca is excited about the transition.

"We have a great relationship and he's very different to Roosy," Petracca said.

"(Goodwin) probably uses a bit more of a teacher-student type learning approach. Roos is a bit more old-school and sometimes gives a few sprays but his mentality is really good, Roosy, and he's positive.

"With Goody, he's just understanding a bit more of relationships and obviously he's played in our generation, so he understands what it takes to make it a bit more."

The most famous spray Petracca received from Roos was after the 20-year-old broke a toe playing basketball.

Petracca, drafted at No. 2 in 2014, had not made his debut because of a ruptured ACL sustained in his first pre-season.

Goodwin had nothing to say about the crack Petracca suffered in the little toe of his right foot, although a fellow assistant had a positive spin on the incident.

"Brendan McCartney said it's actually a good thing because (it means) you can hold your knee back a few more months," Petracca said.