West Ham play "very brave" football and are one of eight teams challenging for a place in Europe, Everton manager Roberto Martinez has said.
The teams meet on Saturday at Goodison Park with the Hammers in fourth with 18 points, four ahead of the Toffees.
"West Ham have been the most consistent team in the Premier League and it wasn't by accident," said Martinez.
"The way they play is very brave - they've a lot of attackers. It'll be one of our the biggest challenges."
He added: "It is still early days but we still have four teams challenging for the title and eight teams looking for Europe.
"West Ham are one of the big challengers for those places without a doubt."
There are currently four points separating West Ham and Tottenham in 12th.
Meanwhile, Martinez echoed chairman Bill Kenwright's comments in dismissing Roy Keane's claims over his players' fitness.
The Republic of Ireland assistant says he wants to talk to Everton about midfielder James McCarthy and full-back Seamus Coleman, suggesting the club exaggerated the seriousness of the duo's injuries.
The pair missed last month's Euro 2016 qualifier against Germany, but then appeared for Everton four days later.
Martinez said: "A lot of nonsense has been said. The reality is the conversations between the managers of the associations and ourselves are good. The only thing I care about is the players."