Roberts believes Bale has plenty of time on his side to improve.
However, he expects the Welshman to add a much-needed boost to Mourinho's team.
In an interview with Bernabeu Digital, former Tottenham defender Graham Roberts said: "Gareth [Bale] still has a long time ahead of him.
"Real Madrid fans are very picky, but Bale has scored great and very important goals in two Champions League finals.
"Zidane needs to look in the mirror and ask himself: 'Did I make a mistake?'"
Roberts went on to add: "He's brilliant. Gareth is the right signing for Tottenham. He'll definitely give the team a big boost."
The Welshman has officially joined Jose Mourinho's squad but questions remain over his broken relationship with Zinedine Zidane.
Speaking in a press conference recently, the French boss dispelled all rumours of a rift between the duo but the signs we've had so far seem to point in a different direction.
Nevertheless, Bale has been a remarkable player for us over the years - and the stats are there to back it up.
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