Davy Klaassen has endured a difficult start at Everton, after signing from Ajax last summer.
Everton signed Klaassen from Ajax in the summer for a fee of £24 million, as valued by the Mirror, but the midfielder has not shown his top form to date.
Klaassen has looked well off the pace, and swiftly dropped down the pecking order at Goodison Park.
But Koeman insists that Klaassen will come good, even if it takes him a season to settle on Merseyside.
“Klaassen has not had an easy start. [But] There is absolutely no doubt about his qualities,” Koeman said.
“There are so many examples of players who were the best in their country, who were ready for a big transfer, and still found it tough here.
“I know bigger stars than Klaassen who needed an entire season before they could deliver.”
Klaassen badly needs to find his form, as Everton fans are already losing patience with him.
The Dutch international showed that he could be a stand out player at Ajax, but the pace of the Premier League seems to have taken him by surprise.
Klaassen could feature for Everton later today, when they take on Brighton & Hove Albion at the AMEX Stadium.
If Everton are able to pick up the three points, they will move into the top half of the Premier League table.
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