The two sides meet at Stamford Bridge with both teams looking to try to capture a finish in the top four in order to earn Champions League football for next season, with London rivals Arsenal also in the running.
Mate has no doubts that Bale, who won a PFA double last month, is the man who the Blues have to keep their eye on.
"Obviously, it's a vital game for both teams and we'll have to watch one of the best players in the world in Gareth Bale," Mata told The Sun.
"He is in amazing shape and process to be a decisive player for Spurs almost every week. I congratulate him for all his recent awards.
"We now play against Tottenham on Wednesday which is going to be a final again. It's going to be tough but I think we can make it and seal our place in next season's Champions League."
Chelsea host Spurs on Wednesday night.