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Rooney nods in his second goal from close range

Adam Rooney scored a hat-trick as Aberdeen maintained their unbeaten Premiership start with a comfortable win at home to St Johnstone.

The striker glanced in an early opener and added another header from close range on 18 minutes.

His third goal came from a second-half penalty after Ryan Christie was upended.

Frank Ross hit the post late on as the hosts dominated and the win takes them level on points with leaders Celtic.

This was only Rooney's third start of the season but that's no excuse for the St Johnstone seemingly forgetting just how dangerous the most prolific Aberdeen striker of recent times is.

They twice went to sleep defending set-pieces and Rooney ruthlessly exploited that negligence to quickly move into what even at that early stage looked a decisive lead.

To add insult to injury it was former Saints' star Stevie May who provided the telling cross for the opening goal after seven minutes leaving his forward partner to steer in a header from six yards.

That stemmed from a well worked free kick on the left and the second came from an equally well executed corner on the right involving May's lay-off to Ryan Christie.

The on-loan Celtic midfielder's cross was nodded on by Anthony O'Connor to Rooney, who once again found enough space inside the six yard box for his third goal of the season.

In fact he might well have had his hat-trick by then as only a desperate blocking challenge prevented the Irishman adding to his tally just prior to that as St Johnstone's normally reliable defence buckled under pressure.

That was exactly the start Dons manager Derek McInnes was looking for in terms of intensity but also the ruthless streak to go with it after being held to a draw in their previous home game against Kilmarnock for not converting initial dominance into sufficient goals.

Rooney made a strong claim for a regular starting place with a strong performance and three goals

The visitors struggled to make any impact going forward in the continued absence of Michael O'Halloran, with the only bit of good news being that the player on loan from Rangers should be back after the international break.

By contrast Aberdeen's pace and variety of attack was a constant threat and only an impressive save from Alan Mannus two minutes from the interval denied Christie the chance to add to the tally from 20 yards.

St Johnstone manager Tommy Wright took action at the break to try and change things, sending on Chris Millar and David Wotherspoon for Scott Tanser and Paul Paton and the second period was much more equal.

The problem for the Perth club was that although they limited Aberdeen's chances to score they also failed to create any clear cut opportunities of their own, so Joe Lewis in the home goal had a quiet afternoon.

To round off a miserable afternoon for St Johnstone, substitute Danny Johnstone tripped Christie deep inside the box and Rooney completed the scoring from the resulting penalty kick with 10 minutes remaining.

Having joined Celtic on the 20 point mark, Aberdeen also pulled six points clear of Saints and Rangers below them.