Spartak scout Dmitri Popov told the Daily Record: "I was not completely impressed by Donati. I did not like him too much and thought that he was possibly a bit overweight.
"One thing about Donati is he is very tactically aware and always in his correct position on the field but I doubt he will have a major role for Celtic at this moment. I preferred Scott Brown."
The Russian scout insisted the Hoops won because of substandard fitness levels in the SPL.
Popov said: "I have been left with differing impressions of Celtic.
"For one hour and 15 minutes, the ordinary provincial team from Falkirk played at the same level as Celtic. They were not worse. They led the game 1-0 and even Celtic's equalising goal came about by accident.
"The game was mostly quiet because even when Celtic were losing they seemed sure they would win. That is most likely the same scenario with every game they play in the SPL.
"What I can say to everyone is Spartak is NOT Falkirk and that will not happen to us."