The Spanish midfielder expects Chelsea to find their form quickly in the wake of the dismissal of Andre Villas-Boas as manager on Sunday.
Juan Mata believes Chelsea can still achieve their targets
Villas-Boas was dismissed as manager on Sunday following the 1-0 defeat at West Bromwich Albion on Saturday, culminating a poor run of form that has seen them win only five of their last 16 Premier League games.
Chelsea are fifth in the league table, three points adrift of fourth-placed Arsenal, and Mata, who was brought to Stamford Bridge in the summer by Villas-Boas, said it was important that they found their form, starting at St Andrew's .
"I think we have to start again," the Spaniard told Chelsea TV.
"We are not in a good moment, we are not in a good run of results, but we all want to change it. I think we are ready to change it.
"We have a very good squad and we have two months to achieve our objectives in the Premier League, in the FA Cup and Champions League."
Roberto Di Matteo, who was installed as first team coach until the end of the season following the removal of Villas-Boas, has added Eddie Newton, a former Chelsea player, to his back-room staff.
Newton, who won the FA Cup, League Cup and the European Cup Winners' Cup during his time with the London club, operated as the Italian's assistant manager when he was he in charge of both MK Dons and West Bromwich Albion.
Newton said: "I can't talk about what has been done before, but I am Chelsea through and through and we want that drive and that will to win, and when we get that, it becomes a habit again."
Chelsea announced that Steve Holland would remain as the assistant first team coach and Christophe Lollichon as goalkeeping coach, while Chris Jones steps up to the role of first team fitness coach following the departure of Jose Mario Rocha.
Daniel Sousa, the chief opposition scout, has also left Chelsea.
Chris Hughton's Birmingham will look to inflict more misery on Chelsea tonight, but the manager of the Championship said he had sympathy for Villas-Boas's fate.
"I think it [eight months] is no time for a manager," he said. "It's a club very much going through a transitional period and I felt he needed time to finish the job he wanted to complete.
"They obviously viewed him as someone for the future but, in that event, you have to give them time to develop.