Bale has not played for Real Madrid since the 3-2 El Clasico loss to Barcelona in April due to a ankle injury he suffered in the first half of the game.
The Welshman has won the Champions League twice already in his career at the Bernabeu and would make it three in four years with a victory over Juventus tomorrow.
The final is taking place in Bale's home city of Cardiff which was extra motivation for him to be fit for the game.
Rush believes Juventus will be scared of Bale, even if he starts the game as a substitute.
Ian Rush believes Gareth Bale could be vital for Real Madrid against Juventus Gareth Bale in Real Madrid training ahead of Champions League final Wed, May 31, 2017
Express Sport brings you the best pictures from Real Madrid's latest training session ahead of the Champions League final against Juventus
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Real Madrid were hard at work in training ahead of the Champions League final
It would be the icing on the cake for Gareth Bale, people seeing him in Real Madrid colours
Ian Rush on Real Madrid star Gareth Bale
"I think even a 50 per cent Gareth Bale would be worth having on the bench," he said on Sky Sports.
"He hasn't played for seven weeks, whether you play him from the start for 60 minutes because he will tire or maybe bring him on after 60, 70 minutes.
"I think if you're the Juventus defenders playing and you're doing really well for 60 minutes and you see Gareth Bale come on you're thinking 'oh God, I've got a problem here'.
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Gareth Bale has got himself fit for Real Madrid's Champions League final against Juventus
"It would be the icing on the cake for Gareth Bale, people seeing him in Real Madrid colours.
"He could come on, score the winning goal, what better story could you ask for?
"I wouldn't put it past him because he's good enough to do that."