According to the Daily Mail, West Ham have doubts over a deal for Alex Song - because the midfielder may have to undergo surgery this summer.
Song, 27, spent last season on loan at West Ham having failed to make an impression at Barcelona, but endured an up-and-down season at Upton Park.
The Cameroonian powerhouse was superb in the first half of the season, dominating games in the middle of Sam Allardyce's midfielder, but his performances deteriorated in 2015.
Those displays led to some Hammers wanting Song to be sent back to Barcelona rather than complete a permanent deal - but recent reports from Sky Sports suggested that West Ham are close to sealing a deal to keep the ex-Arsenal star in East London for good.
However, the Daily Mail report that Song has an injury that could required surgery - meaning West Ham now have doubts over the proposed deal to sign Song permanently.
Worth a permanent move?
West Ham have already snapped up midfielder Pedro Obiang from Sampdoria this summer, and with the likes of Cheikhou Kouyate and Mark Noble also in the reckoning, West Ham could afford to take a gamble on Song recovering in the long-term.
If West Ham feel that Song can recover from his injury and return to the best of his ability, the Hammers could complete the permanent deal and go with their existing options in the meantime.
Song's performances last season divided opinion, but if new manager Slaven Bilic can get the best out of him, a permanent move would be great for West Ham.