West Ham will be without Enner Valencia for up to 12 weeks and the club admit there remains a possibility he may yet require an operation.

The 25-year-old forward was injured after giving West Ham the lead in the Europa League qualifying draw with Astra Giurgiu. West Ham conceded a late own goal as they were pegged back 2-2 by the Romanian side.

The club said on Friday the Ecuador international, who was given oxygen on the pitch, had suffered what “appears to be a significant injury to his right knee and right ankle” and refused to put a time on his return before a meeting with a consultant.

Following that meeting Stijn Vandenbroucke, the club’s head of medical and sports science, confirmed Valencia could miss up to three months. Valencia took to social media to suggest he does not need surgery but Vandenbroucke did not rule out the possibility completely.

He told the club’s website: “Enner visited the consultant on Monday morning, when we discussed the results of the scans he underwent on the injury last Friday. The outcome is that there is now a very small chance he will need an operation and that we instead hope to treat the injury to his fibula using conservative treatment, which we hope to start in three weeks.

“We will know for sure whether or not Enner will need an operation next week but if everything goes to plan we hope he will be available for selection again within 10 to 12 weeks. Enner will spend the next three weeks in a walking boot and using crutches, after which we will start his rehabilitation.”

Valencia took to Instagram to post a picture of himself from the Astra game and wrote that he does not need surgery. He wrote: “I would like to thank everyone for the support and the affection shown on this difficult moment. Thanks God, today I received great news as I won’t need surgery, all the best!”

However, with the club’s record signing Andy Carroll out injured, Slaven Bilic is still likely to sign another striker before the transfer window closes. He has Diafra Sakho, Mauro Zárate and Mobido Maïga available for the return leg in Romania and the Premier League opener at Arsenal on Sunday.

A loan move for the Atlético Madrid and Mexico forward Raúl Jiménez has been widely reported but the 24-year-old would require a work permit before making the move to Upton Park.