Berbatov scored 27 goals in 70 appearances for Tottenham, before moving to Manchester United in 2008.
The Bulgarian won the Premier League golden boot with the Red Devils in 2011 and was something of a cult hero amongst both sets of fans.
In a column Berbatov has written for Betfair, he claims that Manchester City aren't playing good enough football to win the Champions League.
"Manchester City are the favourites to win the Champions League but they wouldn't be my bet to lift the trophy next May," he wrote.
"City ended their Group stage campaign by beating Dinamo Zagreb 4-1 this week but we shouldn't read too much into City's results so far, as they haven't played any opponents that are at their level."
Berbatov believes that Guardiola is hell-bent on winning the Champions League, but that his team are being outplayed so far.
"Pep Guardiola is desperate to win the Champions League with City but other teams are playing better football," he continued.
"Liverpool haven't been at their best in the Champions League this term but they're performing brilliantly in the Premier League and, as the holders, know how to pace themselves for the knockout rounds."
The 38-year-old went on to say that his old club Spurs could have another run like they did last year.
"Barcelona and Juventus are also strong contenders and you shouldn't write off Spurs," Berbatov said.
"They have no reason to be fearful about who they get in Monday's knockout stage draw."
He cites new boss Jose Mourinho as a being a big factor in their potential success.
"In Jose Mourinho, Spurs have a coach who's won trophies throughout his career, including the Champions League with Porto and Inter - two teams that few people would have fancied," he remarked.
"So it doesn't matter who Spurs face. They have great quality and after reaching the final last year, should feel confident."
NOW TRY...
Quiz! Can you name the last 50 scorers in Arsenal vs Manchester City games?
Megan Rapinoe hails "exceptional and composed" Raheem Sterling
