Portugal forward Joao Felix joined Chelsea on loan from Atletico Madrid on Wednesday in a deal that will keep him at the Premier League club until the end of the season.
Felix has also extended his contract with Atletico for one more year until June 2027.
"Chelsea is one of the great teams in the world and I hope to help the team reach their objectives, so I am very, very happy to be here and very excited to play at Stamford Bridge," the player said.
Felix became the third most expensive player of all time when Atletico triggered the 126 million euro (around $140 million) buyout clause in his contract in 2019 to sign him from Benfica.
The 23-year-old Felix is no longer a guaranteed starter under coach Diego Simeone, but Atletico still moved to extend his existing deal.
"From Atletico de Madrid we wish Joao Felix every success in this new professional stage," the Spanish club said in a statement. Felix will hope to rediscover his best form at Chelsea, which has been struggling for attacking inspiration in a poor run of recent results that has left manager Graham Potter under pressure.
Chelsea has now signed four players in January - Ivory Coast forward David Datro Fofana, Brazilian midfielder Andrey Santos and France defender Benoit Badiashile had already joined this month - but Felix is by far the most high profile.Felix adds to the vast array of attacking options at Potter's disposal, fitness permitting, with the Portugal international - who played in four of the country's five matches at the World Cup in Qatar - competing with Raheem Sterling, Christian Pulisic, Pierre-Emerick Aubameyang, Kai Havertz and Hakim Ziyech for a place in the forward line.
Felix never fully fulfilled the expectations that came along with his high-profile transfer in 2019 to replace Antoine Griezmann, who had left Atletico to join Barcelona. Then 19, Felix was considered by many in Portugal as the successor to Cristiano Ronaldo and Atletico fans expected him to become one of the team's biggest stars.
His lackluster first season was blamed mostly on him needing more time to adapt to playing in a top league. He won the Spanish league championship with Atletico the following season despite struggling with injuries and not having a key role in the title campaign. He has since shown spurts of greatness but hasn't played consistently at the level that fans had hoped to see from him.
His departure comes amid reports that he became increasingly at odds with Simeone, who has repeatedly denied having any problems with the player.