Young Czech soccer defender Tomas Kalas has transferred from Sigma Olomouc to Chelsea, Czech media said on Wednesday. Nevertheless, Kalas, 17, will continue playing the top Czech league with Olomouc in the next season as a guest, his agent Pavel Zika said. 'I have never seen such high interest of the biggest clubs in a Czech player,' Zika said. Another club from the Premier League, Arsenal, and Leverkusen from the German Bundesliga were among the clubs that were interested in the player. Thanks to Kalas's transfer, Sigma Olomouc and Chelsea have launched cooperation in exchange stays for young players, Zika said. 