Joao Felix immediately joined his Chelsea team-mates in training at Cobham after joining the club on loan until the end of the season.
Chelsea officially announced the signing of the Portuguese international from Atletico Madrid, having paid £9million for the short term loan.
Felix was pictured in Blues training after his move was finalised, with the Chelsea needing the 23-year-old to hit the ground running to help address their recent poor form.
Chelsea are waiting for a response from the Premier League on whether Felix will be registered in time for their derby with Fulham on Thursday.
The Blues will hope Felix will be available for selection having been struck by an injury crisis in recent weeks.
Chelsea boss Graham Potter believes the signing of Felix will be a lift for the club and hopes attacker can adapt quickly to life in the Premier League.
'He's (Felix) been training and had game time, so from a physical perspective he can go in. It's always a bit of an unknown going from one country to another but how long that takes goes from player to player,' Potter said.
'I see a confident player and one that can impose himself on the game. He can take the ball, take it in tight spaces, make passes. He is a nice addition and I'm really looking forward to working with him.'
Felix joined the Atletico Madrid about £120million - one of the most expensive deals of all time - from Benfica in summer 2019, however has struggled in the Madrid side.
His performances for Benfica, as an 18-year-old, sparked interest across the world as Felix recorded 15 goals and seven assists in his first year in the Portuguese top-flight.
Since making the move to Spain, Felix has scored 34 goals in 131 appearances - which is underwhelming return for the young talent.
Felix is Chelsea's fourth January signing, following the additions of Benoit Badiashile, Andrey Santos and Datro Fofana.
Chelsea confirmed Felix trained alongside fellow forwards Pierre-Emerick Aubameyang and Kai Havertz, as well as new faces Fofana, Badiashile and Gabriel Slonina.
Potter said Aubameyang had missed Chelsea's 4-0 FA Cup third round loss to Manchester City with a back problem.
The Gabon striker's future has appeared uncertain after he had been brought off the bench in the league match against the Premier League champions last week, before being substituted after a dismal showing.
Full backs Ben Chilwell and Reece James were pictured in individual training, as the England internationals seek to step up their recoveries from injury.
Their return to action would represent a significant boost for the club, after a challenging period.
Chelsea will hope to address a run of six defeats in their last nine in all competitions when they travel to Craven Cottage tomorrow to face Fulham.
The Blues currently lie 10th in the Premier League, three places below their local rivals.