*Aston Villa delivered a blow to Chelsea’s title ambitions by inflicting a second successive away defeat on the pre-match Premier League leaders.* Chelsea took the lead when Brad Friedel failed to deal with a speculative long-range effort from Didier Drogba, but they failed to capitalise. An unmarked Richard Dunne headed the home side level after Ashley Young’s corner flicked off Frank Lampard. James Collins headed the winner from another Young corner to stun Chelsea. It was Collins’ first goal in four years as Chelsea’s defence was uncharacteristically exposed again at a set piece. Two seasons ago, Chelsea owner Roman Abramovich left Villa Park before the end of a 2-0 defeat by Martin O’Neill’s side. Two weeks later then manager Jose Mourinho was dismissed. Current Blues’ coach Carlo Ancelotti has no concerns as far as his job security goes, but he will have been deeply unhappy with the lack of concentration at the back which allowed Villa to get back into the game. Villa, with frustrated England striker Emile Heskey again confined to the bench by O’Neill until the final eight minutes, should take plenty of confidence from a hard-earned victory. After a quiet opening, the game exploded into life when emergency referee Kevin Friend - called in at the last minute after Steve Bennett was taken ill - waved away Villa appeals for a penalty. On closer inspection, Jose Bosingwa had wrapped his arm all over Gabriel Agbonlahor’s shoulder, preventing him from capitalising on Stilyan Petrov’s cross with only Petr Cech to beat. Chelsea, fortunate not to concede a penalty, quickly poured forward, James Milner denying Florent Malouda with a smart tackle. But on their next attack the west London club took the lead. Drogba skilfully turned Collins, but was still about 35 yards out when firing his shot at the Villa goal. Friedel should have had the effort comfortably covered, but the 38-year-old American was deceived by the dip and bounce of the shot, and had to hide his embarrassment as he picked the ball out of net. Chelsea, no doubt fortified by the goal, tended to offer more in the way of a threat going forward - so it was a bit of a surprise to see Villa grab an equaliser. It had an element of fortune about it, as Lampard’s attempted clearing header from Young’s corner served up a chance on a silver platter for Dunne. The Republic of Ireland defender buried his header from close range. But Chelsea now produced their best football of the half. Friedel, atoning for his earlier error, had to back-pedal furiously to tip a cheeky chip from the consistently excellent Deco over the top right-hand corner. And a neat move of short passes played across the edge of the Villa area presented Drogba with an excellent chance, whereupon Collins produced a terrific block, throwing his body into the path of the shot. The Blues’ defence was found wanting early in the second half, however, when another corner from Young proved too much to deal with. This time the winger picked out Collins on the far post, who was given vast swathes of undefended territory in which to rise up to nod the ball down, back across goal and into the net. John Terry reacted by jumping around the box like a toddler with a tantrum, but the only way Chelsea could respond was to attack once again. The danger signs were posted when Deco, and then Malouda, failed to test Friedel adequately when each was given an excellent chance to equalise. Though they were now dealing with scraps of possession, with 18 minutes to go Villa had a chance to go 3-1 up. Young swept a beautiful pass from deep on the left flank to Milner on the right. But his lay-off to John Carew was hit over Cech’s bar. Friedel made his third vitally important save of the half when denying Nicolas Anelka, but Deco and Lampard were giving Villa plenty more nervous moments. Chelsea, who had already replaced Bosingwa with Branislav Ivanovic, now sent on Joe Cole for Malouda but seemed to lose their shape as their hunt for an equaliser grew more desperate. Villa comfortably protected their lead during three minutes of added time to leave Chelsea with plenty to think about before the visit of Atletico Madrid in the Champions League on Wednesday. *Aston Villa manager Martin O’Neill:* “We can definitely compete. We’ve a lot of good players in the team and it was a great effort against a top-quality team. My view is that anybody who finishes in front of Chelsea will win the Premier League. “Set pieces are part of the game - World Cup finals have been settled on set pieces - but that tended to overlook what we can do. We try to get it wide and we’ve got players who can electrify the crowd.”