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Spain midfielder Juan Mata is expected to arrive at Manchester United on Friday for a medical ahead of his proposed move from Chelsea.

United have had a bid of around £37m accepted for the player, who is set to sign a four-and-a-half-year deal.

Mata, 25, has failed to command a regular starting place at Chelsea under manager Jose Mourinho.

Mata, who has won 32 caps, said goodbye to team-mates and staff at Chelsea's Cobham training ground on Wednesday.

Mata at Chelsea 2011-12: 54 appearances, 12 goals, Champions League winner, FA Cup winner 2012-13: 64 appearances, 20 goals, Europa League winner 2013-14: 17 appearances, 1 goal (Stats are for all competitions)

United continue to deny having made a bid for the playmaker, but it is understood they have made an offer through intermediaries working on the deal.

Manager David Moyes declined to answer questions on Mata after his side's League Cup semi-final defeat by Sunderland.

Should the deal go through, it would break United's previous transfer record of £30.75m they paid Spurs for Dimitar Berbatov in September 2008.

On Tuesday, Chelsea insisted that Mata, who had been voted the club's player of the year two seasons in a row, was not for sale.

But the player, who was part of the Spain squad which won the World Cup in 2010 and European Championship in 2012, has been substituted in nine of his 13 Premier League appearances for the Blues this season.

Analysis Phil McNulty Chief football writer "The club-record move for Juan Mata is not only a sign of ambition and support for manager David Moyes - it is a sign of the urgency with which improvement is required. "United get a player who will add much-needed quality and creation to their out-of-sorts side. "The intrigue surrounds where Moyes will play Mata if and when all his attacking resources such as Wayne Rooney and Robin van Persie are fit again. The Spain attacker's best position is just behind the strikers, so how will Moyes adjust his team to fit him in with the gifted Adnan Januzaj also available?"

United have made no secret of their plans to rebuild their team under Moyes and are prepared to pay a premium for top players if it means securing them now rather than waiting until the summer.

"A lot of the work we are doing now is in preparation for the summer," Moyes told United's matchday programme ahead of the Sunderland game.

"If we can do any business now, then we will certainly try to do it, but I will not compromise the standards required for a player that can come into this club and help improve it."

Mourinho, 50, said last week that while he understood it was "hard" for Mata to sit on the bench, the Spaniard still had a "big role" to play at the club.

The Portuguese has trusted Eden Hazard, Oscar and summer signing Willian in attacking roles this season and while his relationship with Mata is healthy, he has conceded Chelsea's system does not suit the player.

"There are fantastic players, but sometimes the fantastic players are more fantastic to a certain system and less fantastic in a certain model of play," Mourinho told BBC Sport's Football Focus.

Mourinho on Mata's future (Football Focus)

"He is an unbelievable player and a fantastic boy who is trying his best to adapt."

Chelsea paid £23.5m to sign Mata from Valencia in 2011. The former Real Madrid youth player began life in England by scoring 13 goals in his first at Stamford Bridge won the FA Cup and Champions League.

He followed it up with 20 goals in the 2012-13 season as Chelsea lifted the Europa League under Rafael Benitez but, since Mourinho returned for his second spell at the club, Mata has seen his playing time limited.

He was substituted 53 minutes into the Blues' 3-0 win at Southampton on New Year's Day, his last appearance, and was visibly frustrated when taking his place on the bench.