Tony Docherty, the Aberdeen assistant manager, acknowledged last night that David Goodwillie is now producing his best form for the club as a result of the faith shown in him by the management team at Pittodrie.

The 25-year-old arrived at the club during the close season in need of confidence following an unimpressive spell with Blackburn Rovers, a club he had joined for £2m.

His time at Ewood Park was punctuated by loan moves to Crystal Palace, United and Blackpool, but none of them led to a permanent transfer until Aberdeen offered a one-year contract during the summer. The work Goodwillie has since put in during training sessions has led Docherty to refer to the forward as a "true professional".

Goodwillie has relinquished a starting place to Adam Rooney of late, but there is no doubt that the one-time Scotland internationalist's contribution since making the move has been valuable.

"Adam and David have both been fantastic since they came to the club," said Docherty, who worked with Goodwillie while coaching at Tannadice. "It was a tough decision which striker to go with against Hamilton last Wednesday and against Ross County on Monday night.

"Sometimes it works for you and sometimes it doesn't. But Goodie's attitude is fantastic. He is ready to come on and contribute if required, as he did against County.

"People underestimate how good a professional David Goodwillie is. He is a top professional. We are fortunate to have good professionals at the club who we can pick and choose from depending on the opposition."

The next team that Aberdeen face is Celtic. The champions will visit the north east on Sunday and Derek McInnes is satisfied with Aberdeen's formidable defensive record ahead of the match, with his side keeping clean sheets in each of their last three league games.

"It was great to get a third clean sheet on Monday night," said the Aberdeen manager. "Keeping clean sheets is important to us."