Former Chelsea player Yuri Zhirkov has praised the impact of Guus Hiddink following his return to the club last month.
Chelsea are unbeaten in eight games following the sacking of Jose Mourinho, seven of those under the stewardship of Hiddink, and have pulled away from the Premier League relegation zone.
Hiddink is refusing to give up on the top four, even though Chelsea are 14 points behind Tottenham Hotspur, and Zhirkov is confident the club have hired the right man.
Zhirkov played under Hiddink for four years when he was in charge of Russia between 2006 and 2010. But he joined Chelsea in the summer of 2009, just weeks after the Dutch coach's previous interim spell had culmintaed in FA Cup final success.
"I know Hiddink and I have no doubt that once he took over, the atmosphere at Chelsea became so much better and more relaxed than it had been before," Zhirkov told Reuters.
"The reason for the recent poor run is psychological. A year ago, Chelsea won the championship and this has had a bearing on the next season.
"When you win the title, it is also difficult to defend it and to play at the highest level.
"I think with Guus, Chelsea will ride out the crisis and next season will be back at the top of the table."
Zhirkov also spoke fondly of Chelsea owner Roman Abramovich.
"He is a really nice and simple person. Abramovich is able to get on well with everyone and he often comes to the training ground and even played table tennis with us," he added.
"Of course it was difficult when I was not playing, but on the whole, I was happy with that period. I won a championship medal -- that says it all."
On Tuesday, Zhirkov signed a precontract agreement with Zenit St Petersburg and will join on a free transfer from Dynamo Moscow on July 1.