Gary Cahill expects the battle for the Premier League title to be far more challenging this season after Chelsea's rivals splashed the cash in an attempt to dethrone the London club.
Jose Mourinho's side won the title at a canter last term, finishing eight points ahead of previous champions Manchester City.
City have reacted by signing England internationals Raheem Sterling and Fabian Delph, while Manchester United have brought in the likes of Bastian Schweinsteiger, Memphis Depay and Morgan Schneiderlin.
Arsenal are also predicted to be among the contenders after luring Petr Cech from Chelsea, with Arsene Wenger expected to do further business before the transfer window shuts at the end of this month.
Mourinho has added Radamel Falcao and Asmir Begovic to his squad, but Chelsea centre-back Cahill is anticipating a more closely fought title race.
He said: "I think if you look at last season we were strong as it was. We have strengthened. I don't know what else is going to happen from now until the end of the window.
"I'm unsure. You've seen last season that collectively as a group we were strong. There's a lot of young players here and we're okay. Other teams have gone out and spent money and it will be very tough.
"It is tough ever single year and it's no different and with them strengthening it makes it even harder. We just need to go about our business and get in the best possible condition to start the season and try and do what we did last year.
"We're the team that everybody wants to beat as well. We had that feeling as well when you're playing against the champions. When Man City were the champions and we were playing against them there is that added bit where people want to beat you.
"Even just being at a club like Chelsea people want to beat you anyway. I'm sure the other lads at the top will feel the same way. There'll be that as well. Everyone wants to go out and win against you, so it's going to be tough.
"There's no way of dressing over it, it's going to be hard, the Premier League is always hard. It's long. You have to be consistent for a long period of time so it's difficult but we're looking forward to it."
Chelsea face Arsenal in the Community Shield at Wembley on Sunday before starting their title defence against Swansea City next Saturday.
