Czech defender Tomas Kalas has agreed a one-year contract extension on improved terms to stay at Chelsea until 2017.
The 19-year-old centre back, who switched to Stamford Bridge from Sigma Olomouc two years ago, will also spend another year on loan at Vitesse Arnhem, where he made 33 appearances and scored one goal in last season.
The teenager is delighted to agree his now deal with the Blues.
"By this Chelsea have shown me that they count on me in the future and I think high of it. They have come themselves with the offer to extend my contract and improve the terms for me," he told CTK.
"At the same time, we agreed that it would be best for me to spend one more year at Arnhem to get more experience. I believe it will help me and I will return to Chelsea even stronger."
After joining the Blues, Kalas returned on loan to his Czech club for six months before he spent half a year in the Academy.
Last year, he became a regular starter and an important player for Vitesse Arnhem and he returned to Holland on Wednesday after spending time in preparation with Chelsea.
Kalas's agent Viktor Kolar said: "That is also why the interest in him from top Dutch and German clubs arose
"Chelsea have clear intentions, though, and by extending his contract they have demonstrated it."