Juan Mata is close to completing a £40m move to Manchester United, after telling Chelsea on Wednesday morning that he wanted to leave and sitting out training to guard against injury.

United have indicated a readiness to pay what will be a club-record fee for the 25-year-old Spain midfielder, having identified him as the player to spark their season, and all parties have come to view the deal as the best way forward.

Chelsea will consider whether to move for Internazionale's Colombia midfielder Fredy Guarín, particularly as they might sanction a loan for Michael Essien – the midfielder is a target for Galatasaray. United are expected to loan the winger Wilfried Zaha to Cardiff City once the Mata deal has been concluded.

United have moved quickly for Mata and the player's father and agent, Juan Sr, is in England to oversee the final stages of the negotiations. Mata, who joined Chelsea in 2011 for £23.5m from Valencia, is set to sign a four-and-a-half year contract at Old Trafford.

His star has fallen dramatically since José Mourinho took over as the Chelsea manager last summer. Mata had been Chelsea's player of the year in his first two seasons but he has struggled to impress Mourinho, who has long held reservations about the midfielder's lack of pace, physical presence and defensive ability.

Mata was furious to be substituted at Southampton on New Year's Day and he has not played since. Under Mourinho, he has started 11 of the club's 22 Premier League games. Mata needs more regular football to make sure of his place in Spain's World Cup squad.

He reported to Chelsea's training ground in Cobham on Wednesday but his work there is effectively over. He is fully fit but he went through a routine away from the first team.

Mourinho has sought to rebalance his squad this month. Kevin De Bruyne, the attacking midfielder, has been sold for €20m (£16.4m) to Wolfsburg while the defensive midfielder Nemanja Matic has arrived for £20.75m from Benfica. With Mata and possibly Essien also leaving, the pursuit of Guarín would appear shrewd, particularly as he could be available for a bargain €10m.

Guarín, who Mourinho has long admired, is a versatile, attack-minded central midfielder. He had agreed terms on a switch to Juventus, with the striker Mirko Vucinic set to move in the opposite direction, only for Inter fans to voice their vociferous disapproval. The swap was called off but Guarín was left dissatisfied and Inter are keen to sell before the end of the month.