Southampton manager Ronald Koeman on Thursday backed Oriol Romeu to prove his worth in the Premier League after the Spanish midfielder signed from Chelsea on a three-year contract.

Romeu, 23, completed a £5 million ($7.8 million, seven million euros) move late on Wednesday after spending the last two seasons away from Chelsea at Valencia and Stuttgart.

Romeu joined Chelsea from Barcelona in 2011, but a serious knee injury sustained in December 2012 saw him lose his place in the first-team hierarchy.

However, Koeman is convinced he has what it takes to thrive in the English top flight, telling a press conference: "He's a very good player.

"(He is) 23 years old, played already in the Premier League, had a good season in Stuttgart last year and he makes the team stronger.

"It's not easy to be a player in the first XI of Chelsea because they have so many good players and for young players it's difficult. It's always up to the manager, the confidence of the player.

"I think it's the right moment for the player to make this move to Southampton because he will play more for Southampton than for Chelsea."

Koeman missed Southampton's 2-2 draw at Newcastle United last weekend after undergoing surgery on his Achilles tendon, but will return for Saturday's home game with Everton.