Chelsea defender Kalas joins Cologne on loan

The Czech, who has a solitary international cap to his name, spent two seasons on loan at Dutch outfit Vitesse Arnhem before returning to Stamford Bridge for the 2013-14 campaign.

After being handed his Chelsea debut as a late substitute in a 2-0 League Cup win at Arsenal in October, Kalas made his European bow in a last-16 home triumph over Galatasaray.

Kalas' first start for the club came in the huge 2-0 Premier League victory at Liverpool in April, and he was among the starting XI once again on the last day of the Premier League season at relegated Cardiff City.

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