LONDON -- Chelsea boss Jose Mourinho has said he has already achieved his primary transfer target this summer in retaining key stars Eden Hazard, Nemanja Matic, Cesc Fabregas and Diego Costa.
Mourinho underlined his desire to sign a striker, midfielder and defender to bolster the squad but indicated that he is satisfied with the core of his squad.
"My first target this summer is done," he said at the launch of the new BT Sport European football channel. "That is to keep the players I want to keep. In other seasons, I was happy to sell players, even if they were obviously good players. Not this summer.
"I keep Hazard, Matic, Fabregas, Diego -- all these important guys. That is the first start."
Mourinho, who has suggested he could look to take a player in exchange if backup goalkeeper Petr Cech moves on, repeated that he plans to find a replacement for departing striker Didier Drogba as well as increasing the depth of his squad.
"We will look to sign a striker as we lost our legend," he said. "[Chelsea also want] a defender and a midfield player to add some competition to the squad. It puts some pressure on the players as they know they have someone behind waiting.
"I need that to support my way of work. We want competition, but we are the champions and we want stability at the club."
While Chelsea eased to the Premier League title as well as winning the Capital One Cup, Mourinho said there was no room for complacency.
"We have to improve," he said. "If we are the same team, the others will be better than us. We have to be better, but that does not mean we have to buy a lot. We have preseason to try and improve and we can be stronger in all areas.
"The status of being champions has to be positive and we will have more confidence and experience."
Chelsea's European campaign was less successful as they exited the Champions League to Paris Saint-Germain at the round-of-16 stage.
No Premier League club made it to the quarterfinals this year as English clubs' struggles on the continent continued.
Mourinho, who has also won titles in Portugal, Italy and Spain, said it has become more difficult for English clubs than some of their rivals in European leagues because of the lack of a winter break.
"When I was in Spain and Italy, I missed English football so much," he said. "Despite playing at Christmas -- and with the amazing Boxing Day fixtures -- I miss it, but the reality is that after Christmas, we are tired and sometimes not just physically and also mentally.
"It is more difficult for English clubs. What is the answer? Bigger squads? With the financial fair play, it is not so easy, unless you have an owner to pay the punishment for you. Our owner doesn't want [to do that]. I agree with him -- rules are rules.
"Maybe after Christmas, after Boxing Day, we can give the players a bit of a break at that point. Players are human beings and too much football is difficult for them."