Antonio Conte has warned that Chelsea must bring in more players to have any chance of successfully defending their Premier League title.
The Blues are interested in a string of others including Southampton centre-back Virgil van Dijk, Arsenal's Alex Oxlade-Chamberlain, Leicester midfielder Danny Drinkwater and Valencia right-back Joao Cancelo.
Asked if it will be hard to retain the title this season without making more signings, Conte told Sky Sports Premier League: "Yes, for sure. This league is not easy. Six teams are very strong and you must be prepared.
"I hope to be able to improve our squad. The transfer market is not finished. We want to be competitive and we want to fight for the title again. The club knows my priorities.
"It's a great challenge for us to try and retain the title, but we are working hard."
One player whose future at Stamford Bridge is in doubt is striker Diego Costa, but Conte remained tight-lipped on whether the Spain international will still be at the club next season.
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"The way I think about Costa is the same," he said on the Premier League launch show. "I think I was very clear; it's not important to repeat it."
The Blues did allow midfielder Nemanja Matic to join rivals Manchester United this summer, a departure Conte described as "a great loss".
"Matic knows very well what I think about him," he said. "The importance for me about this player, who is a really good player, a top player, very important for our team, but sometimes you must accept this crazy transfer market.
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"And sometimes you must accept different decisions. But he is a great loss for us."
Chelsea also spent a club record £70m to sign Morata this summer and Conte has revealed the striker is in contention to start his first Premier League game at home to Burnley on Saturday.
"Alvaro is a really good player, he's still young despite having a lot of experience," he said.
"He needs to play regularly, he's a player I trust a lot. I think he has good prospects for Chelsea - for now and the future.
"Will he start this weekend? He's working very well and starting to understand or idea of football."