According to Sky Sports, the Spain Under-23 international is undergoing a medical with the Saints today after a transfer fee was agreed between the two clubs.
His move will not be temporary; rather, he is expected to head to the St Mary’s Stadium permanently.
Sky Sports claim that the deal could be announced later today.
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The 23-year-old joined Chelsea from Barcelona in 2011, signing a four-year contract.
While his career in west London got off to an impressive start, a serious knee ligament injury left him sidelined for eight months, and sadly signified the end of his career with the reigning Premier League champions.
With the likelihood of sitting behind Nemanja Matic, Cesc Fabregas, Oscar, Ramires and John Obi Mikel in the pecking order, a transfer away from the club arrives with little surprise, and is unquestionably the best option for his career.
He has spent the past two seasons on loan at Valencia and VfB Stuttgart.
With Morgan Schneiderlin having been sold to Manchester United this summer, Ronaldo Koeman is in need of strengthening his midfield, and having been nurtured at Barcelona’s academy as a youngster before his move to Chelsea, Romeu could be the perfect signing for Southampton.