Juan Mata arrived at Manchester United’s training ground by helicopter on Saturday and was met by manager David Moyes ahead of completing his proposed transfer from Chelsea.
The Spain midfielder, 25, was then set to undergo a medical before becoming United’s club-record £37m signing.
Mata must be registered by noon on Monday to be available for United’s home game against Cardiff on Tuesday.
Moyes later left the training ground to watch Cardiff in action against Bolton.
Several United players used social media to welcome Mata to the club.
Defender Rio Ferdinand tweeted: “Welcome to my amigo..! Hoping you enjoy your time here and help continue the success at this club.”
Their previous transfer record was the £30.75m paid to Tottenham for Dimitar Berbatov in 2008.
Mata, who joined Chelsea from Valenciafor £23.5m in 2011, has been Chelsea’s player of the year in each of the last two seasons.
However, he has failed to command a regular starting place under Jose Mourinho, who returned to Stamford Bridge last summer for a second spell as manager.
“The player deserves respect and to play and because the offer is right, we allowed him to negotiate,” Mourinho said on Friday.
“Things are going in a good direction. We have allowed Juan to travel and have the medical.”
Mata, who has won 32 caps for Spain, said goodbye to team-mates and staff at Chelsea’s Cobham training ground on Wednesday.
Mourinho has trusted Eden Hazard, Oscar and summer signing Willian in attacking roles this season and, while his relationship with Mata is healthy, the Portuguese conceded Chelsea’s system does not suit the player.
Mourinho said: “I asked Mata when the offer came whether he really was happy to go and he said ‘yes, I am really happy to go’. After that we could feel mixed emotions.
“This is a fantastic opportunity for him. Another big club wants him in the country he wants to stay in, has made the right offer for him, so, although lots of clubs feel you should not sell to rivals, we are different.”
“I think this club is a special club and it cares for people. It is very respectful of its players and especially those who wrote history and Juan is one of these.
“He was fantastic for Chelsea and Chelsea was fantastic for him. We are not afraid he is going there to do very well. We want him to go there and be happy.”
It was reported that Mata’s move would be delayed until Chelsea completed the signing of Mohamed Salah from FC Basel.
However, the 21-year-old Egypt midfielder still needs to accept personal terms, undergo a medical and receive a work permit.