Czech midfielder Jiri Jarosik has completed a move from CSKA Moscow to Chelsea on a two-and-a-half year deal.
Jarosik (L) has faced Chelsea in the Champions League this season
Jarosik agreed a long-term contract and will move to Stamford Bridge for a fee believed to be in the region of £3m.
"I'm very happy and proud to have joined a club like Chelsea - it's like a dream come true for me," Jarosik, 27, told the club's official website.
"I hope I will become an important part of the squad and help Chelsea to achieve their goals for the season."
Jarosik is eligible to play immediately for Chelsea, but he will not be able to take part in the Champions League having already played in the competition for CSKA.
The midfielder began his career at Sparta Prague before moving to Moscow in January 2003.
Jarosik's agent Viktor Kolar likened his client to Arsenal skipper Patrick Vieira, and emphasised Jarosik's extensive Champions League experience.
"He's a versatile player who can play in midfield or attack - he's very tall, very similar to Patrick Vieira," he said.
When he was originally set to move to Stamford Bridge, Jarosik enthused: "There is a great chance for me here and I will do everything to take it.
"Jose Mourinho explained the situation in Chelsea to me and said that I will certainly be given my chance.
"He said he had chosen me because he needed a midfielder, who is not too young nor too old."