Chelsea will play Werder Bremen in Germany on August 7 as part of their pre-season preparations.
Melvyn Lorenzen will miss the first three weeks of Werder Bremen's pre-season training after being attacked on his doorstep.
Veteran striker Claudio Pizarro has signed a new one-year contract with Bundesliga side Werder Bremen.
Chelsea loanee Papy Djilobodji is being investigated by state prosecutors in Germany for making a throat-slitting gesture.
Werder Bremen moved out of the Bundesliga's bottom three after a thumping 6-2 win over Stuttgart on Monday.
Two goals from Pierre-Michel Lasogga gave Hamburg a vital win against relegation rivals Werder Bremen on Friday night.