West Ham United boss Sam Allardyce has warned fans lightening may not strike twice inn terms of the transfer market.

He explained, writing in the London Evening Standard: "It's particularly rewarding when one of those gambles pays off for everyone, but it's difficult to see how you can keep doing it without threatening the club's growth.

"Admittedly, the £8m-£10m player represents a risk that you are going to have to take more often than in the past because there are far fewer top players around.

"Diafra Sakho, at a lot less than that sum, could prove to be a one-in-a- million signing. Likewise Enner Valencia and Cheikhou Kouyate have made bright, encouraging starts.

"We've been outstanding with our recruitment success rate this season but that doesn't automatically mean it's going to be the same next summer.

"We'd love it to be the case but realistically it's unlikely that future signings will have quite the same impact on improving the team as last summer's intake, although we live in hope."