Fulham academy chief Huw Jennings is delighted with the U20 World Cup participants.
On Frei, Jennings told fulhamfc.com: "If you take Kerim Frei, he decided recently to represent Turkey and I think for someone such as Kerim, with such a mixed heritage, for him to make that decision is obviously a key factor in his development.
"He's already had opportunities with the Turkish senior team and now he's going to get into a tournament with the Under-20 team, and it's going to be great experience for him.
"Kerim had a difficult season because he had two major injuries and that's set him back. He didn't get the amount of appearances that he would have liked, and I think he knows that it's a big season coming up for him at Fulham. So to have this almost as part of his pre-season programme, having had such a long period out, will be really good for him. And for it to be for the home nation, as well, is even more significant."