The Blues face testing Premier League clashes against Manchester United on Sunday before the visit of London neighbours Tottenham on Wednesday.
And despite having already booked their place in the Europa League final against Benfica in Amsterdam later this month, Spain star Mata says the club must focus their attentions on qualifying for Europe's elite competition.
He told the Daily Star: "We have to get in the top four. We have to win these two games.
"We want Champions League football next season. After that we can try to win another trophy.
"There are two tough games ahead. Playing Tottenham is going to be like a final because both teams will be fighting for the same thing.
"If we can beat Tottenham it will be a big step forward.
"But before that we have to think about Manchester United."