Diego Costa and Cesc Fabregas are only going to improve on their outstanding debut seasons for Chelsea, Cesar Azpilicueta has warned the club's Premier League rivals.
Jose Mourinho brought the duo to Stamford Bridge ahead of the 2014-15 campaign, and both players played central roles in helping the club lift the title.
"We know their quality and despite what they did last season, they want to do better," he said.
"They are competitive and have a winning mentality. They will not just settle for what they did before and will want to do more.
"The season they did before was amazing, but they are looking to go even further than they did before for Chelsea.
"That should worry the other teams. What they do is key for us. The amount of goals and assists these two players give us make the difference.
"The numbers they did in their first season was amazing and can be again."
