Fernando Torres turned down the chance to take Chelsea's 70th minute penalty in their FA Cup replay win at Birmingham City, which might have allowed him to end his near five-month scoring drought.

Chelsea were 2-0 up and coasting into the quarter-finals on Tuesday night when Torres was fouled by Guirane N'Daw inside the area. Juan Mata, the designated penalty taker, offered the kick to Torres, his friend and fellow Spaniard, only for the 27-year-old to decline. Although Daniel Sturridge subsequently tried to claim the ball, Mata stepped up to the spot and saw his shot saved by Colin Doyle.

Torres rarely takes penalties but his refusal to accept this one offered the latest illustration of his crisis of confidence. The striker's link-up play was again good, on his 50th appearance for Chelsea since a £50m move from Liverpool, but he continued to snatch at anything in front of goal.

He dragged a first-half chance wide and his descent to figure of fun was reinforced during the interval, when a Birmingham fan missed his kick in the half-time competition. "It was worse than Torres," he told the on-pitch interviewer, to much hilarity. The St Andrew's crowd chanted "We want Torres" upon the award of the penalty. The forward, who has five goals in all competitions for Chelsea, has not scored in 23 matches.

"I asked him if he wanted to take it because he provoked [won] the penalty," Mata said. "He said: 'I'm not first on the list to shoot,' so that's what happened. It was because he forced the penalty and I gave him the chance. Robbie [Di Matteo, the interim manager] put a paper with who shoots penalties and that was it."

Chelsea continue their search for a permanent managerial replacement for André Villas-Boas, who was sacked on Sunday, and the club's hierarchy noted the anti-Rafael Benítez chants that came from the visiting enclosure at St Andrew's.

The former Liverpool manager has advanced his candidacy and has suggested he could help to restore Torres to his former glories, having overseen him during their time together at Anfield. But Chelsea's directors are not thought to have him under consideration.

Chelsea's players were told by the owner Roman Abramovich, in the wake of Villas-Boas's dismissal, that they have to raise their game and there was the sense at Birmingham that the message had gone through.

"He [Abramovich] said that we have an opportunity to change the run of defeats and against Birmingham we did so," Mata said. "We have to prove ourselves every game. For me and the other players, we are playing in a top squad and a top club, and we must always do our best in every game.

"There is a lot of unity in the dressing room. No matter who the manager is, we are all focused on the same objective. We must do the best for the club ... we belong to the club and we will do everything for the club. Every one of the players will do it. We will try to win this FA Cup and also against Napoli [in the Champions League last-16 second-leg]. I think we can do it – it is possible for us to win 2-0 [to advance on aggregate]."