Celtic manager Gordon Strachan insists Scott McDonald's new-found maturity encouraged him to give the Australian striker a second chance by bringing him to Parkhead.

Strachan freed the 24-year-old when he was boss of Saints but bought him back from Motherwell for £700,000 in the summer after the little striker had spells at Huddersfield, Bournemouth and MK Dons.

McDonald will partner Jan Vennegoor of Hesselink in tonight's Champions League qualifying second leg against Spartak Moscow at Celtic Park.

The SPL champions snatched a 1-1 draw in the Luzhniki stadium a fortnight ago and the Hoops boss will pin his hopes on McDonald helping Celtic join Rangers in the draw for the group stages.

Strachan claims he simply exercised his right to change his mind when he signed the striker.

He said: "Scott's more respectful and a better person. Before, he was a boy being a boy, a young kid away from Australia.

"He's more understanding about the coaches and players about him.

"He understands that people around him will make him a better player, especially the players.

"Sometimes people have to go away and progress, grow up and he's grown up immensely.

"Remember at the time I had good strikers like James Beattie, Marian Pahars, Kevin Davis and Brett Ormerod.

"He wasn't really getting a game then and was getting frustrated with himself. He had to go and grow up.

"You can change opinions surely? It's not the 10 Commandments.

"Everyone changes their opinions about players sometimes.

"I did what was right at the time. Since then he's improved".

McDonald admits his attitude was less than perfect when he was at Saints and the former Motherwell player praised Strachan for changing his original evaluation of him.

He said: "I was only 15 when I came over on my own to sign a professional contract with Southampton for three years.

"I made my debut when I was 18 in the Premier League under Stuart Gray.

"When you are young you think you have done enough and that you've made it.

"But that's not the case and you get the shock of your life when someone turns around and tells you that you're not good enough.

"It's hard to bounce back from that but it drives you on and you want to prove people wrong. Obviously I've done that.

"It shows the true character of the manager that he re-signed me.

"I must have done something right and he sees something in me.

"How many managers would take back a player they have knocked back before?

"But there was never an issue with me and the manager. We never fell out.

"It was just a matter of me not being in his plans. He had a good squad and felt I was never going to get an opportunity and that I needed to go somewhere else.

"He did me a favour in the end. I managed to get first team experience elsewhere, I improved as a player and that's why I'm here now".