A costly error at the back has gifted Chelsea a 1-0 lead over Aston Villa at half time in their Premier League meeting.
The hosts were the side looking to set the tempo early on, but their opponents got away the first shot of note when Carles Gil fired over the bar at the end of a free kick.
A much-changed Chelsea side, without the likes of Nemanja Matic, Gary Cahill or Eden Hazard from the off this afternoon, themselves pushed forward and got in an attempt of their own through Ruben Loftus-Cheek on his first start of the season.
One of those to benefit from the first-team overhaul, Baba Rahman, was then overpowered by Alan Hutton down the flank which allowed the Scotsman to drill in a shot which Asmir Begovic kept out, before the rebound was was fired wide.
Villa were looking more confident at this stage, and came forward once more in a move that culminated in Rudy Gestede picking out Jack Grealish to drill in a rather tame shot on goal.
Summer signing Jordan Ayew then tried his luck, sending a free kick narrowly over the target, before Ramires fired a set-piece attempt of his own straight into the wall up the other end.
Just after seeing the Villans squander arguably the best opening of the game through Gestede's headed chance, Chelsea were able to capitalise on a sloppy piece of play at the back from their opponents to make the breakthrough in West London.
Brad Guzan's poor pass to Joleon Lescott was cut out by Willian, who simply picked out the returning Diego Costa to tap home from close range.
Buoyed by that, Willian had another pop at goal with a curled effort that Guzan had less trouble with on this occasion, while Kieran Westwood and Grealish could not truly trouble Begovic as the visitors upped the ante.
Costa wanted a penalty at the end of the opening 45 minutes, but the officials adjudged that Kieran Richardson made little contact on the Spain international inside the box.