Charlie Nicholas has issued an apology to Aaron Mooy after he questioned Celtic's signing of the midfielder in the summer.

The Australian international was brought in by Ange Postecoglou and at the beginning of his Hoops journey it was clear he was struggling for match fitness and sharpness.

But since the World Cup break Mooy has gone on to become a key former for Celtic and his midfield performance have already made him a favourite with supporters.

Nicholas was quick to write Mooy off when he secured a move to Celtic and now he has admitted that he got his transfer prognosis wrong.

He wrote in the Daily Express: "I have to hold my hands up and admit Aaron Mooy has silenced me and the rest of his critics by becoming a massive player for Celtic. When he arrived last July, I was wondering what Ange Postecoglou had done. I knew the pair had worked together previously with the Australian national team but Mooy looked a yard off the pace in his first few weeks for the Hoops.

"He seemed to slow the play down and I didn't see how he was going to fit into Postecoglou's team, which loves to play with speed and moves the ball about constantly. At that point I wasn't talking about the 32-year-old midfielder's fitness, more his game management. I know Mooy hadn't played for several months before he pitched up at Parkhead, but in a lot of his early games I just couldn't see what he was going to bring.

"He did get fitter and sharper but the real catalyst was the World Cup, where he performed really well for Australia. Mooy has looked a completely different player since coming back from Qatar. He is completely transformed. He's been the best player in the country since the restart and has scored five times in the last seven games.

"He is now a vital cog in Celtic's attacking play, a major goal threat and has forged a great partnership with captain Callum McGregor. That is testament to Mooy himself and Postecoglou for putting his trust in him.There is now real competition in the engine room, with Reo Hatate also in there.

"Matt O'Riley is a top player and until recently he was one of the first names on the teamsheet. But even he is no longer guaranteed to start in this Celtic side."