*Diego Costa’s outstanding start to his career at Chelsea continued as he grabbed his eighth goal to help the leaders to victory against Aston Villa.* The Spain striker then created another as Jose Mourinho’s side secured their fifth win of the season. Oscar was first on the scoresheet when he tapped in after Willian’s shot was saved by Brad Guzan. Costa added a second with a header before his jinking run and shot led to Willian’s goal from close range. Although the scoreline suggests it was a stroll for Chelsea, for long periods the attack had been suppressed by a disciplined Villa defence. Nevertheless, even against a stingy backline, the Blues added another three goals to this season’s tally to remain the league’s leading scorers with 19 in six matches. The win also means Mourinho’s team are one of four unbeaten sides across all the four divisions with 16 points from a possible 18. They took a while to insert their dominance against Villa, so would have been grateful for the breakthrough in the seventh minute. On that occasion, full-back Branislav Ivanovic slipped a pass down the left into the path of Willian, whose initial shot was saved by American Guzan. However, the ball returned to the former Shakhtar Donetsk midfielder who found Oscar, with the 23-year-old adding the final touch from close range. Up until the second goal, Villa had kept up with Chelsea’s attack and restricted them for space. Costa, in particular, looked a frustrated figure in attack. Doubts still surround whether he has fully recovered from a hamstring injury, although he showed how effective he can be with careful management. He should have scored in the first half, when he headed Willian’s brilliant delivery straight at Guzan. However, he beat the Villa keeper with a similar effort just before the hour mark. With his tail up, Costa appeared to move with more purpose and a dazzling run in the area led to the third. Cesc Fabregas, who had a quiet game playing in a deeper midfield position, delivered a sumptuous cross-field pass for his Spain team-mate. The former Atletico Madrid striker confused Philippe Senderos with his footwork before firing a low shot that was saved by Guzan, but then poked in by Willian. Costa was brought off to a standing ovation. He is already proving to be an integral figure in Chelsea’s title challenge. Villa, whose best chance came in the first half when Aly Cissokho hooked wide, face another stiff test next week - at home to Manchester City.