Aberdeen manager Derek McInnes has seen Sam Cosgrove's ability rocket with confidence.

The striker took his season tally to 15 goals in 16 matches with an exquisite finish in a 3-0 victory over Motherwell.

Cosgrove opened the scoring in the 15th minute at Fir Park when he raced on to Greg Leigh's through ball and chipped Mark Gillespie.

Cosgrove was 17 games into his Dons career before he netted his first goal following a £25,000 move from Carlisle in January 2018.

But the 22-year-old ultimately ended his first full season with 21 goals and is well on his way to smashing that total.

McInnes said: "He has done probably the last thing you'd expect, but having the confidence to do that... When he first came from Carlisle, I said to him he would have put that over the stand.

"He would probably never have got there because he probably didn't have the confidence, the power to go and show himself the way he is.

"People can take credit for his progression but it's him. He has done it, he has taken an opportunity. Somebody took a chance on him and he's run with it.

"His ability is getting better and better and his confidence is clearly making him the player he is.

"A number nine thrives on that confidence. I played with number nines who you heard as soon as you walked into the stadium for training, they strolled about, bowled about.

"That's him just now. He is walking about as if he can do no wrong. His goal epitomised that.

"He is carrying that mantle of being Aberdeen's number nine and that's not an easy thing to deal with coming from where he came from, but he is doing it absolutely brilliantly at the minute.

"He looks at times unplayable. He has actually been under the weather the last few days and been feeling a bit lethargic but there was nothing lethargic about his performance.

"He is really imposing himself on centre-backs. He is in a good place just now, his link play, his running power, the quality of his finishing, his heading ability, he gives you a bit of everything."

Aberdeen's triumph came despite defenders Leigh and Zak Vyner starting in central midfield amid a selection crisis.

Vyner netted the third after Niall McGinn had doubled Aberdeen's lead, both also producing expert finishes.

Motherwell boss Stephen Robinson was left to bemoan individual errors from his Scotland Under-21 trio.

James Scott had an early penalty saved by Joe Lewis, Barry Maguire allowed Cosgrove to get past him for the opener and Allan Campbell was robbed by McGinn near the edge of his box.

"I keep hearing Aberdeen have injury problems, there weren't too many inexperienced players in Aberdeen's team," Robinson said.

"We are not going to be too hard on ourselves. I thought there were boys who were five or 10 per cent down after they came back from international duty, which happens at times.

"We will live and learn, we are still sitting third. It was three very young boys who made individual errors, they will learn from it and get better from it."