Chelsea manager Jose Mourinho has declared Juan Mata will continue to be a fringe first-team player until he adapts to the club's new style.
Mata, who was Chelsea's player of the year for the last two seasons, has struggled to break into the starting XI since Mourinho has taken over at Stamford Bridge.
The sporadic use of the Spaniard has perplexed Blues fans but Mourinho has made no apologies for his decision and says Mata has work to do if he is to become a regular starter.
Mourinho hinted Mata, who wants to play in the 'number 10' role, had to be prepared to play in a wider role and says Oscar is the first-choice for that position behind the lead striker at the moment.
"The way I'm reading the situation and the reasons why, in this moment, he's (Mata) not playing so much are things I can speak about with him but not publicly," Mourinho said on Friday.
"But he played against Everton from the start and you can analyse his performance. He came on against Basel when the team were winning 1-0 – not like Demba Ba or Mikel John Obi, who came on to rescue the game –with specific tasks to do.
"It's part of a process with him, too. It is one thing to play with Ramires and Oscar closing down opponents on each side, and Mata as a number 10, behind a striker with his clever assists, clever passes and fantastic actions because he has great talent.
"But it is another thing to adapt to the way we want to play. In this moment, Oscar is my number 10 and, if anyone tells me Oscar has not been Chelsea's best player this season, I'd have to disagree.
"I have to prove to the fans that I am good. Now (Mata) must do the same."
Mata, who has been a key member of the Chelsea side that has won the UEFA Champions League and UEFA Europa League over the last two seasons, has featured in just three matches under Mourinho.
Along with Oscar and Eden Hazard, Mata was regularly part of an exciting attacking triumvirate behind a lone striker last season, and Mourinho says there is no reason that cannot be successful again.
"But only when (Mata) adapts to what we want," Mourinho said.
"I'm not ready to ask Oscar to track opposing full-backs. Brazil has more talented players in the number 10 position than any other country in the world, and he plays there for the national team, so I want to build with Oscar as my number 10.
"I want the other two players, from the side, to adapt to that reality and learn how to do things they were not ready to do before.
"The players are open to some of the changes.
"If I'm an attacking player I'd prefer to play without a position, without certain responsibilities, and with others behind me to cover so I don't need to worry about (tracking back). It's about changing mentality.
"It takes a bit of time. But it won't take five, six, seven years. I promise."
Mourinho also said the Blues slow start to the season, which includes back-to-back losses in the Premier League and the Champions League, is due to a change in the team's playing style he is trying to implement.
"I don't like the way Chelsea were playing the last couple of years; the club doesn't like it and we want to change," the Portuguese said.
"We want to play a different style. The past is history – even my past. I'm here like I've just arrived."
|Berisha extends Victory stay|
|Arnold backs fans amid A-League boycott|
|Perez happy at Newcastle|
|Klopp can´t forget ´f***ing´ Palace loss|
|Mihajlovic: Milan didn´t expect extra time|
|Carvalhal hopes cup run spurs Wednesday to league success|
|Coppa Italia Review: AC Milan survive scare, Torino thrash Cesena|
|Hughes happy with rotation policy after League Cup win|
|Football League Review: Burton win to go top of League One|
|Atletico still uncomfortable - Simeone|
|AC Milan 3 Crotone 1 (aet): Bonaventura and Niang extra-time strikes send hosts through|
|Leganes 2 Granada 1: Segunda Division side threaten upset|
|Ligue 1 Review: Leaders Paris Saint-Germain held on the road|
|City thrashing cruel on Hull - Bruce|
|City thrashing cruel on Hull - Bruce|
|Pellegrini: Silva brings style back to City|
|Reaching last four is ´terrific´ - Martinez|
|Lukaku urges Everton to push on|
|FIFA sponsors call for ´independent oversight´ of reforms|
|Stoke City 2 Sheffield Wednesday 0: Potters end visitors´ League Cup run|
|Manchester City 4 Hull City 1: De Bruyne double books semi-final spot|
|Middlesbrough 0 Everton 2: Deulofeu and Lukaku on target in routine win|
|Reus Deportiu 1 Atletico Madrid 2: Third-tier hosts make life difficult for Atleti|
|Amnesty International critical of Qatar, FIFA|
|Angers 0 Paris Saint-Germain 0: Cavani fails to make his mark|
|Ramos: Madrid fight for Undecima every day|
|Silver screen awaits for Vardy?|
|Del Bosque noncommittal on Aduritz form|
|Dybala: Juventus´ slow start normal|
|Koeman confident Southampton can match Liverpool|
|Venezuela stars issue quit threat to FA|
|Moreno agent opens door to Real Madrid offer|
|Herrera: I´m very happy at Manchester United|
|Lars Bender undergoes ankle surgery|
|Delneri takes over at Verona|
|Bellerin: I did not know how to defend until I joined Arsenal|
|Panathinaikos hit with three-point penalty after violence|
|Martial and Depay unhappy under ´selfish´ Van Gaal - Parker|
|Injured Carvajal set to miss Cadiz tie|
|Klopp vows to play strongest Liverpool team against Southampton|
|Ronaldo rested for Copa clash|
|Sanchis implies Neymar provoked Isco kick|
|Benitez: I have no problem with James|
|Luis Enrique plays down Suarez Ballon d´Or omission|
|Sergio Ramos is right - football is cyclical, says Luis Enrique|
|Klopp defends Mignolet amid Ter Stegen rumours|
|Boksic backs Mandzukic to get 20 goals for Juve|
|Neymar hails ´great friends´ Messi and Suarez|
|Chelsea submit planning application for new stadium|
|French sports people need to be exemplary - Valls|
|Moyes: Valencia job has come too soon for Neville|
|Napoli loss ´doesn´t change anything´ for Mancini|
|Ronaldo ´uncomfortable´ as a number nine, claims Madrid great Sanchez|
|Manchester City receive $400m Chinese investment|
|Messi: Ronaldo deserves Ballon d´Or nomination, but I´d prefer Suarez|
|Moyes open to another European gig|
|Everton welcome cup pressure - Martinez|
|Casillas open to MLS move|
|Hughes: Butland going nowhere|
|Milner eyes trophies at ´exciting´ Liverpool|
|Napoli became anxious - Sarri|
|Inter did not deserve to lose - Mancini|
|Messi beats Ronaldo to top prize at La Liga awards|
|Bolton Wanderers 1 Brentford 1: Smith watches on as strugglers snatch point|
|Napoli 2 Inter 1: Higuain at the double as hosts go top|
|Lewandowski: Less pressure on me than Aubameyang|
|Defoe, Larsson to miss Arsenal match|
|Sassuolo 1 Fiorentina 1: Di Francesco´s side extend unbeaten home run|
|Barcelona took ´a step forward´ without Messi - Busquets|
|Unfair to blame Garcia for Roma form - Zanetti|
|Southampton v Liverpool: Returning stars have Ibe in buoyant mood|
|Lewandowski´s five-goal haul recognised for four records|
|Barcelona v Villanovense: Holders get second crack at minnows|
|Verona sack Mandorlini|
|Valencia confirm Nuno departure|
|Premier League clubs reveal agent fees|
|Stoke will not underestimate Sheffield Wednesday – Hughes|
|Robben wants Guardiola to stay at Bayern|
|Aguero allays foot injury concerns|
|Cadiz v Real Madrid: Pepe calls for hard work in Andalusia|
|Bolton confirm players have not been paid for November|
|Neville takes Valencia training following Nuno resignation|
|Mihajlovic targets Coppa Italia triumph|
|Garde confident Villa will survive|
|Everton to make late call on Barry and McCarthy|
|Davids: Messi is an anomaly but Ronaldo just an athlete|
|Simeone open to January signings following Tiago injury|
|Messi leads nominees for Puskas Award|
|Hummels defends himself after media criticism|
|Messi, Ronaldo and Neymar nominated for Ballon d´Or|
|Luis Enrique, Guardiola and Sampaoli up for World Coach of the Year|
|Chelsea about the team, not just Costa - Ivanovic|
|Kuyt open to Feyenoord extension|
|Barcelona lodge complaint over ex-Madrid duo´s Neymar comments|
|Davies wants Manchester City quarter-final to get crazy|
|Ribery ordeal is over – Rummenigge|
|Smalling: Vardy run opens door to non-League hopefuls|
|Bender relieved to end Dortmund losing streak|
|Mata: Manchester United have six finals in December|
|Vardy reveals painful road to Premier League record|
|Pardew urges Newcastle to back McClaren|
|Russian clubs banned from signing Turkish players|
|Klopp expects Coutinho to face Southampton|
|Valverde: Let´s hope Barcelona don´t sign Aduriz|
|De Bruyne relishing link-up with Silva|
|´Crazy´ Munich could convince Guardiola to stay|
|Defiant Garcia refuses to resign despite Roma slump|
|Monk confident Swansea can turn the corner|
|Bellerin: Arsenal can cope without Sanchez|
|McClaren: Newcastle not panicking|
|Klopp delighted with Sturridge, Henderson returns|
|I wouldn´t swap Lukaku for Vardy - Martinez|
|MLS Review: Timbers, Crew to meet in final|
|Nuno saddened by Valencia departure|
|Morata will become a key player - Allegri|