Sam Allardyce has urged his West Ham United defenders to avoid any confrontations with Chelsea striker Diego Costa when the two sides meet at Upton Park on Wednesday.

Costa's aggressive approach often attracts criticism, but the 17 goals he has scored so far in his debut Premier League season has been a key reason behind Chelsea's success.

Speaking in his pre-match press conference, Allardyce revealed his admiration for the Spain international and admitted that his side must not give him extra motivation.

"We're not to get involved with him, our central defenders are not to get involved with how he might upset them," the Hammers boss told reporters.

"People say he's an old-fashioned centre forward because he seems to get motivated by the physical and niggly aspect of it so we're not to get involved in that.

"I don't think it winds him up - it winds him up to make him better which is a silly thing to do."

Costa scored as Chelsea won the reverse fixture 2-0 in December.