Aston Villa midfielder Stiliyan Petrov claims Chelsea are "not the team they used to be." Third-placed Villa could open up a five-point gap if they can triumph at Villa Park 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." Petrov will be hoping Villa have learnt lessons from the 2-0 defeat they suffered at Stamford Bridge 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." Midfielder Steve Sidwell will be available to face his former club after being suspended for the Uefa Cup clash with CSKA Moscow in midweek. Striker Emile Heskey and winger James Milner are battling to recover from Achilles and thigh problems respectively. Skipper Martin Laursen, Carlos Cuellar, Wilfred Bouma and Nigel Reo-Coker are still ruled out.