The Spanish duo arrived from La Liga this summer, impressing fans and pundits with influential displays, and the Chelsea star believes there is more to come from the pairJuan Mata is happy to see compatriots Michu and Santi Cazorla make an impact in the Premier League, and feels that they are yet to reach top form.
Michu, a £2 million signing from Spanish outfit Rayo Vallecano, has taken to the English top-flight superbly, scoring four goals in just three appearances.
And Cazorla, who Arsenal signed for £16 million from financially-stricken Malaga, impressed for the Gunners on Sunday, scoring one and assisting Lukas Podolski's goal in a 2-0 win.
"I'm very happy for them, they are doing very well. And they are going to play even better" Mata said after receiving an award from his hometown club, Club de Campo La Fresneda.
Meanwhile, Mata believes that Chelsea can challenge for all competitions this year despite losing 4-1 to Atletico Madrid in the Uefa Super Cup.
The Blues are looking to be the first club to successfully retain their Champions League and are also seeking to challenge for the Premier League crown. And while the Spain playmaker says it would be historic to secure back-to-back Champions League triumphs, he concedes it will be tough.
"We lost in the Euro Super Cup in a bad game," he added. "In the Premier League, we've already played three good games. But I hope we can defend the Champions League title.
"To win again it would be something for history. We got a tough group, but we expect to reach the second phase."
Chelsea were drawn into Group E with FC Nordsjaelland of Denmark, Serie A champions Juventus and Ukraine outfit Shakhtar Donetsk as they begin their Champions League title defence later this month.