Everton signed Klaassen from Ajax in the summer transfer window, but the midfielder has endured a torrid start at Goodison Park.
The Dutch international has looked off the pace when given a chance in an Everton shirt, and has quickly dropped down the pecking order.
Klaassen did not even get off the substitutes’ bench yesterday, as Everton lost 1-0 to Burnley.
And Barton also has concerns over whether Gylfi Sigurdsson will be able to live up to his record breaking transfer fee.
“Klaassen looks a dud,” Barton bemoaned. “Sigurdsson hasn’t hit the ground running, not much to my surprise.
“I never consider him that calibre of player. I think he needs to be a big player in a small team, but at Everton the team isn’t built around him so he can’t showcase the talent.”
Sigurdsson and Klaassen have both faced fierce criticism at Everton so far, with both facing a battle to win the doubters at Goodison Park over.
The Toffees summer spending caught the eye, but so far things have not worked out for many of Koeman’s additions.
Everton are currently in 16th place in the Premier League table, and look to be badly struggling to find their strongest line-up.