Petr Cech's switch to Arsenal makes Chelsea's rivals stronger, and midfielder Nemanja Matic is displeased.
Chelsea midfielder Nemanja Matic is unhappy Arsenal signed Petr Cech and hopes the goalkeeper fails to live up to his previous high standards.
Cech, 33, ended an 11-season stay at Stamford Bridge by joining Arsenal in June for a reported fee of £10million.
The move will only strengthen Arsene Wenger's men, who finished 12 points adrift of champions Chelsea last season.
Matic wished Cech all the best, but would prefer the Czech Republic international performed below expectations.
"Petr is a great guy and a great keeper. It is going to be a very important signing for them,” the Serbia international said.
"But I am not happy because of that. We know that he is very professional. He is one of the best keepers. And I hope this season he does not perform as he did here for 10-11 years.
"I am happy for him because he gets to stay in London, which for him and his family was very important. I wish him all the best."
Matic is confident Chelsea can make it back-to-back Premier League crowns despite few additions in the off-season.
Jose Mourinho has brought in Asmir Begovic and Radamel Falcao, the latter on loan, as his main additions while Chelsea are also trying to buy Everton defender John Stones.
"I think last year Man United, Man City, Arsenal, Liverpool and Tottenham also had good teams, very good teams. Our team was champion and a team that is champion is ready for everything. I think we have enough," Matic said.
"Maybe other teams will sign lots of players but that may be worse for them. It is sometimes better to stay with the same team for stability. I am sure if we stick to doing what we are capable of, we can achieve a lot this season."