The Blues go into the match knowing a second defeat in a fortnight against the Ukrainian Premier League champions would leave them with a mountain to climb to avoid becoming the first reigning Champions League winners to fail to reach the knockout stage.
Mata, who has been one of Chelsea's top performers during the early parts of the season, knows what a stern challenge Shakhtar pose and will treat the meeting as a cup final.
"It's time to move on and to focus on the Champions League match this Wednesday. It's like a final for us if we want to finish first in our group," he wrote on his official online blog.
"Besides, in Ukraine, Shakhtar proved to be a top team who are able to beat anyone. Even so, we always have a great support at the Bridge and I'm confident that we will get a victory to face the last two games in a good position. Champions League's nights at the Bridge are always special."
The Spain playmaker sat out Saturday's 1-1 draw with Swansea with a slight hamstring problem after playing the whole of Chelsea's 5-4 extra-time victory over Manchester United in the Capital One Cup and suggested he just needed to rest up following a tiring week.
"After such a huge effort during 120 minutes I was forced to rest a few days with a hamstring injury," he said.
"That's why I missed our game in Wales vs Swansea."
Summer signing Victor Moses made his first league start for the club at Swansea due to Mata's injury with the former Wigan forward opening the scoring before Pablo Hernandez's late equaliser.
Moses feels he has shown Chelsea boss Roberto Di Matteo what he can do but reckons the team still needs to improve.
"It's a massive club and with the amount and quality of players we have here you have to wait for your chance. That's what I've been doing and I have to show the manager I'm good enough to start. It's just part of the game," he told the club's official website.
"I was delighted to start but the game was a bit slow from us, though we came out second half and dominated, but it cost us at the end. It's not the best result but we have to take it and move on from it.
"Now we have to keep on improving week in week out, but I am delighted to be here."
Defender David Luiz was also ruled out of the draw at Swansea with an ankle injury so the return of captain John Terry could prove to be very timely for Di Matteo.
Terry has just served a four-match domestic ban after deciding not to appeal an FA charge of racially abusing QPR defender Anton Ferdinand.
The former England skipper sat out three league games and the Capital One Cup success over Manchester United.
The Blues conceded 10 goals in Terry's absence and it would seem unthinkable that the 31-year-old will not come straight back into the starting line-up.
A 2-1 loss to reigning Ukrainian Premier League champions Shakhtar two weeks ago leaves Chelsea on four points after three games with a tricky trip to Turin to face Juventus still to come after Wednesday's match.