Lennon's side, who face Lazio in Rome on Thursday, top Europa League Group E and the Scottish Premiership, with a League Cup final place secured.

McDonald concedes he is surprised Lennon has improved the successful squad inherited from Brendan Rodgers.

"You have to fully commend him," the Australian said.

"After the defeat in Europe, the hysterics started and the support was all over the place. [Boli] Bolingoli and [Christopher] Jullien didn't play that game and everyone was saying 'what's going on?'.

"It was a tough ask taking over from Brendan Rodgers, but it just shows what a quality manager Neil Lennon is to get by all that and come out the other end and build his own team now.

"Neil has brought special moments, especially that win against Lazio. They're already in the League Cup final and you wouldn't put it past them to win the treble again."

McDonald fully expects Celtic to progress to the Europa League last 32 for the third season running, even if they suffer defeat in Rome.

"The football they've been playing is phenomenal," he said. "They've still got Rennes to come to Celtic Park, so I'm more than confident they will reach the next stage."

But he sounded a note of caution over the dependence on 21-year-old Odsonne Edouard, currently the club's only fully-fit striker with Vakoun Bayo facing knee surgery and Leigh Griffiths not having played since August.

"They're a bit threadbare up top and heavily reliant on Edouard," said McDonald, who scored 64 goals in a three-season spell at Celtic from 2007.

"You get that one injury to him and you're in bother. There's no question at the moment Celtic will be scouring the world for a top striker. It just depends what funds Lennon has to bring in the right one."