Jol says the former Grasshoppers winger needed to move on to get regular first-team football.
He said: "Kerim has progressed well through his time in the academy and into the fringes of the first team, which enabled him to play for the Turkish national team, which is a big thing for him.
"But for him to continue this progression and to really fulfil his potential he needs to play week in, week out, and I couldn't offer him that as part of the first team here, so we decided to accept the offer.
"He's sure to have a big impact back in Turkey and I know that on a personal level it's a good option for him."
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