Hawthorn legend Dermott Brereton has raised concerns over his former club's ability to return to the finals.

The Hawks missed September action last year for the first time since 2009 and Brereton believes they, alongside Collingwood, are the two most difficult sides to predict in 2018.

Brereton says the positive form of the club without injured veterans makes him unsure whether their return will necessarily boost the team's on-field performance.

โ€œThe thing he (Clarkson) had up his sleeve has already been done last year with Jack Gunston and James Sicily back, and Will Langford as a pressure forward, even though he couldnโ€™t kick the ball through the goals,โ€ Brereton told 1116 SEN on Friday.

โ€œThat worked really well for them.

โ€œThis is a cop out, but I think the two teams that are the hardest to get a read on for 2018 are Hawthorn and Collingwood.

โ€œThe Hawks, after the halfway mark last season, were about the third best performed team.

โ€œThat was when they lost Ben Stratton, James Frawley, Cyril Rioli, and theyโ€™ve had a host of other players, and of course Jaeger O'Meara.

โ€œThey lost all those players, they had 18 operations throughout the season, and they were still the third best performed team after the halfway mark.

โ€œCounteracting that was the fact they werenโ€™t very good when they had those good players in.

โ€œWill they be better with those champion players coming back? I canโ€™t see them dramatically improving.โ€

Brereton was however buoyed by the fact the injury-riddled Jaeger O'Meara played in Hawthorn's intra-club match after a solid pre-season.

The former Suns' midfielder is an unquestionable talent and could be the key to the Hawks revival according to Brereton.

โ€œThere is always concern because of that injury history,โ€ Brereton said.

โ€œIt is a worry about how many games he has been put on the field.

โ€œItโ€™s a concern but if someone is really injured, and theyโ€™re battling away, as per the history of Oโ€˜Meara, you donโ€™t play them in intra-club games.

โ€œSo you have to take it on face value that things are going alright. You just have your fingers crossed the boy is able to get through.โ€

Hawthorn face the Bulldogs and Carlton in the pre-season before meeting Collingwood in a round one MCG blockbuster.