until Mata struck with three minutes remaining at Old Trafford on Sunday to give Chelsea a precious 1-0 victory.
The Spaniard's goal, via a telling deflection off Phil Jones, lifted Chelsea three points above Spurs and means they will be virtually guaranteed a place in next season's Champions League if they defeat their London rivals.
The win over United was Chelsea's 65th game of the season, but with Champions League qualification at stake and a Europa League final against Benfica still to come, Mata says there is simply not enough time for mental fatigue to creep in.
"Three points here (at Old Trafford) is amazing, because now we are in third position. If we win against Tottenham we will be in the Champions League," he said following Sunday's match.
"Mentally you don't have time to disconnect. We play Sunday, Wednesday, Saturday, so mentally you are always focused.
"We need to rest, to train and get ready. We want and need to win against Tottenham."
Had Mata and his team-mates failed to overcome United, Spurs would have travelled to west London knowing that victory would have taken them into the Champions League places at Chelsea's expense.
In any case, Spurs must win to take up a place in the top four.
Victory would come with the added satisfaction of knocking eternal rivals Arsenal out of the Champions League qualifying berths, but Tottenham have not won at Stamford Bridge since February 1990 — a run of 25 matches.
Gerrard to undergo surgery this week
London: Liverpool and England captain Steven Gerrard will undergo shoulder surgery this week that will rule him out of the last two games of the season, the club said on Tuesday.
The 32-year-old, who has been ever present in this season's league campaign, is now likely to miss England's friendlies against Ireland at Wembley on May 29 and away to Brazil on June 2. "The captain's injury has progressively worsened in recent weeks and requires an operation to cure it," Liverpool said in a statement.
O’Shea strike keeps Sunderland afloat
London: John O'Shea scored a second-half equaliser as 10-man Sunderland rescued a 1-1 draw at home to Stoke City on Monday that moved them three points clear of the Premier League relegation zone.
Jonathan Walters gave the visitors an early lead when he reacted smartly in the box to poke home from close range on nine minutes after his header had been blocked.
Sunderland had a player sent off for the second week running when Craig Gardner was shown a straight red card.