Czech starlet, who has a 100 per cent winning record with the Blues, is to play in Germany for a season.
Chelsea centre-back Tomas Kalas will spend the 2014-15 season on loan at FC Cologne.
The Stamford Bridge club confirmed the deal on their official website earlier today.
Kalas, who has made four first-team appearances for the Blues, will officially join Cologne on July 1.
The 21-year-old moved to Chelsea from Sigma Olomouc in 2009, but he has spent much of the past three years on loan at Vitesse Arnhem.
His switch to Cologne should see him test himself against a stronger standard of opposition than in Holland.
Cologne were promoted to Germany’s top division this season after winning the Bundesliga 2.
Kalas, who has been capped once by the Czech Republic at senior international level, made his Chelsea debut in a 2-0 win at Arsenal in the League Cup in October.
He then featured in a 2-0 victory over Galatasaray in the Champions League in March.
Both of his first two appearances had been as a late substitute, but his third outing saw him play the full 90 minutes as Chelsea won 2-0 at Liverpool in April.
He then continued his 100 per cent winning record by playing the whole match as the Blues won 2-1 at Cardiff City in May.
Kalas has three years left to run on his current contract at Stamford Bridge.
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