Sam Allardyce admits he is worried that Manchester United will attempt to re-sign Ravel Morrison.
The highly rated midfielder was shown the exit door at Old Trafford in January last year after a number of disciplinary issues forced Sir Alex Ferguson to sell.
Morrison is now starting to show his potential at Upton Park with a notable solo effort scored at White Hart Lane last weekend a particular highlight.
The youngster was awarded with a call up to the England under-21 team and made his debut against San Marino on Thursday evening.
Manchester United defender Rio Ferdinand reserved special praise for the midfielder after the goal, saying on Twitter: "Great to see Ravel Morrison playing well & focused consistently now. That goal wouldn't make his top 3 goals show reel by the way!"
West Ham manager Allardyce has now admitted the Hammers will struggle to keep the 20-year-old should a big bid come in and has suggested a buy back clause to Manchester United may exist.
"I don't know if there is a buy-back clause and what that figure might be if it even exists," Allardyce is quoted as saying in the Sunday People.
"But my real big worry is that Manchester United will come back to buy him.
"Look at what happened when Chris Smalling played a handful of games for Fulham - United jumped in with £10million.
"Then there was Phil Jones when I was at Blackburn - that's what you are up against."