McDonald has been a shadow of himself in front of goal this season, netting just once so far after scoring 32 goals for his club last season.

Now newspapers and fans in the UK have begin to question his fitness - with some claiming he looks more than 10kg heavier than he did just a few months ago.

Latest pics of the stocky hitman do appear to show him looking barrel-chested compared to the more athletic figure of last season.

Leading Scottish broadsheet The Scotsman has now joined the chorus condemning the little Aussie.

Talking about the goalless Champions League draw with Aalborg midweek, the paper said: "But, to this observer at least, the most questionable inclusion was that of Scott McDonald.

"Despite having scored with a brilliantly-controlled volley against Motherwell four days before, the little Australian striker in that match looked generally sluggish, his frame appearing much too burly for a man of his stature.

"McDonald, at the moment, is nothing like the whippet who contributed 32 goals to last season's championship-winning effort."

Rival broadsheet The Herald quoted one Celtic fan saying: "The players, not the manager, were to blame for Celtic's inability to break down Aalborg. Scott McDonald must be at least two stone overweight."

And the newspaper added: "Georgios Samaras deserved his inclusion on the back of a five-goal spree and did everything but score on Wednesday. Scott McDonald is another matter.

"His success has raised two issues: one over his fitness and another over the psychological toll of his feats.

"Either the new kit is unflattering or the likeable Australian has enjoyed a summer of excess."

It added: "Like John Hartson before him, maintaining a fighting weight is a full-time occupation.

"He is evidently not as mobile as last season."

The Evening Times reviewed McDonald's contribution to the Euro game saying simply: "Last season's main hitman hardly had a sight of goal. But his movement, or lack of it, contributed to this."

Fans have added to the debate, calling McDonald "the big-boned kangaroo..."

One blog added: "Has anyone else noticed that Scott McDonald has put on a bit of weight recently? I'm not suggesting he needs a gastric band fitted or anything but Skippy has put on an extra pound or two during the summer months. Not exactly the brightest idea when your main striking weapon is your pace."