Mata played a key role in the only goal of the game as the Blues beat Manchester United 1-0 at Trafford on Sunday, with his shot deflecting home off Phil Jones.
The victory keeps them on point ahead of Arsenal - with a game in hand - and three ahead of Spurs, and they know victory at Stamford Bridge will confirm a place at Europe's top table next season.
It would put them six points clear of Spurs but their goal difference is so superior that Spurs will not be able to catch them.
"We knew maybe a point wasn't bad (at Old Trafford) but we wanted to win," Mata told Chelsea TV. "We now play against Tottenham on Wednesday, which is going to be a final again.
"Three points is amazing because now we are in third position. If we win against Tottenham we will be in the Champions League.
"Mentally you don't have time to disconnect. We play Sunday, Wednesday, Saturday, so mentally you are always focused.
"Physically you have to rest. These two days are important to us, Monday and Tuesday.
"We need to rest, to train and get ready. We want and need to win against Tottenham."
Interim boss Rafa Benitez feels Mata's influence has been a strong one with the former Valencia player a key contributor in attack.
He said: "Sometimes we have some players growing, and Mata is one of these players.
"I said he could be player of the year, for everything he does for us, scoring goals, giving assists.
"He is a very influential player in the game.
"You can see a lot of the other players growing too. That is what we have to do."
Another of Chelsea's attacking weapons, Eden Hazard, was not risked at Old Trafford due to a tight calf but he could return in midweek.
Benitez said: "I think he could be available but it is not easy to say now. The physios are working with him so we will see."