Cesc Fabregas and Diego Costa have been backed by Cesar Azpilicueta to perform even more outstandingly for Chelsea in the forthcoming season than they did in helping the team to win the title in their first campaign with the club. (Mourinho's Remarks Stir Controversy)
Both were central figures last season, with Fabregas making 23 assists in all competitions and Costa scoring 20 goals in 26 Premier League appearances. (Filipe Luis Set For Atletico Madrid Return)
With Jose Mourinho challenging his squad to justify Chelsea's decision to have a relatively frugal summer in the transfer market by improving as individuals, the pressure is on Fabregas and Costa to deliver.
"We know their quality and despite what they did last season, they want to do better," said the full-back Azpilicueta, a fellow Spain international.
"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."
Costa struggled towards the end of last season with a hamstring problem but has been training here in full flow. "He has been working on this and his fitness and it is already showing in training," Azpilicueta said. "His aim is to be 100% all season from the start to the end."
The Brazilian midfielder Oscar's target is to elevate himself into an elite Premier League performer. Mourinho has challenged the 23-year-old to make waves in the manner of Eden Hazard, whose performances shone like a beacon for much of last season.
"The manager wants me to play like Eden did last year and play at the top level all the season," said Oscar. "I am a different player to Eden. He has his qualities, I have mine. I will try to have my best ever season. I want to do it and Eden will try to.
"Can I win Player of the Year like Hazard did? It is an ambition of mine. I want to do it. I think I have the quality, I am strong in the mind and good with my feet. If I play my best, I will try to win the Player of the Year."