Aston Villa midfielder Stiliyan Petrov claims Chelsea are "not the team they used to be under Jose Mourinho" - but still expects a stern test in Saturday's Premier League clash at Villa Park.
And Petrov admits Villa have much to prove after being outplayed in a 2-0 defeat at Stamford Bridge earlier in the season.
Third-placed Villa would open up a five-point gap if they can triumph in what will be Guus Hiddink's first match in charge of Chelsea.
Petrov said: "Chelsea will be strong. They have a new manager. Every new manager tries to win his first game.
"We expect a very hard game. They will try to show they are still fighting for the title but we won't give up.
"We will try to show them what we have achieved so far is not just because of luck but because of the way we have been playing.
"It is very tight race at the moment and every point from now on will be important."
Petrov added: "Have Chelsea lost their invincibility? When Jose Mourinho was here, they had a special team and they had more belief in themselves.
"They are definitely not the team they used to be under Jose Mourinho.
"A lot of changes have happened there but they will still be strong, they have players to win games. We will try to give them as much respect as we can but we will try to win as well."
Petrov wants to see if Villa have learnt lessons from their defeat against their rivals earlier in the campaign.
He said: "That is the game in which we were really outplayed. They were quicker, faster, stronger than us and it is up to us to see if we have taken anything from that game.
"We will find out if we have learnt from our mistakes, find out if we are we going to be the same. We will see on Saturday.
"We have a lot of points to prove - but first to prove we are not in our situation through luck but through hard work and good play."
Midfielder Steve Sidwell will be available to face his former club after being suspended for the UEFA Cup clash with CSKA Moscow in midweek.