Chelsea manager Graham Potter hailed new signing Joao Felix as a player who could "make a difference" after the Atletico Madrid forward joined the struggling Premier League club on loan on Wednesday.
The Portugal international signed for the injury-hit Blues for a reported fee of 11 million euros ($12 million) as Potter seeks to cut the gap to the top four, which is already 10 points.
Chelsea tweeted "the artist has arrived" as they welcomed the 23-year-old, who had also been linked with Arsenal and Manchester United.
"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," Felix said in a club statement.
Potter said Felix would boost his side's attacking options – Chelsea have scored just 20 goals in the Premier League, less than half of Manchester City's tally.
"He's a quality player. He can make a difference in the final third of the pitch," Potter said.
"He's young but has still had a lot of really good experience. He's just a quality player that gives everyone a lift.
"We've been aware of him for a while – these kinds of things don't happen quickly. The injuries have sharpened the focus a little bit."
Chelsea are waiting to hear whether Felix was registered in time to feature against Fulham at Craven Cottage on Thursday.
Felix joined Atletico from Benfica in 2019 for 126 million euros, making him one of the most expensive players of all time, and has scored 34 goals in 131 appearances for the club, winning La Liga in 2021.
He also featured in Portugal's run to the World Cup quarter-finals in Qatar last month, scoring in the 3-2 victory against Ghana in the group stage.
Also on Wednesday, Atletico confirmed that Felix had extended his contract with the Spanish club for one more season, until June 2027.
"From Atletico Madrid we wish Joao Felix every success in this new professional stage," the Spanish club said in a statement.
Atletico CEO Miguel Angel Gil Marin last month described the forward as a "world-class talent" but said a number of factors, including his troubled relationship with the club's boss Diego Simeone, meant they should look at other options for the player.
"Personally, I would love him to continue but I think that right now the player has other ideas," he said.
Felix becomes Chelsea's fourth signing of the January transfer window after the arrivals of Benoit Badiashile, David Datro Fofana and Andrey Santos.
Potter said there was there was still time for Chelsea to do more business if the right players became available.
"There's time (for more signings)," he said. "Whether we'll find the right players or not is another thing.
"You have to look in this window to make the right decisions, but it's complicated. We're happy with what we've done so far."
Chelsea's new American owners, who took over last May, have lavished more than £300 million ($365 million) on new players to improve a squad that finished third in the Premier League last season.
But despite the heavy spending, Chelsea have endured a turbulent season, sacking manager Thomas Tuchel in September just seven games into the new campaign and replacing him with Potter, who has had to contend with a debilitating injury list.
Chelsea are well adrift of a top-four spot in the Premier League after a miserable run of just one win in eight league games.
They are also out of both domestic cup competitions after a humiliating 4-0 defeat to Manchester City in the FA Cup third round at the weekend but face Borussia Dortmund in the Champions League last 16.