The Welshman, signed from Real Madrid last summer, has started just one Premier League game this season.
And Berbatov believe manager Jose Mourinho has been left unimpressed by the veteran winger.
"I was expecting a lot of him coming to Spurs, to shake things up and for him, Son and Kane to make it a trio up front that can rival the Liverpool attacking trio, for example," Berbatov toldStats Perform.
"For the moment it is 100 per cent not working. Hopefully he can get back to 100 per cent and start playing. If not, in the end it is an easy decision – he can go back to Madrid."