Costa hits double on home debut
Diego Costa struck twice in the first seven minutes of his Stamford Bridge debut to hand Chelsea a 2-0 victory over Real Sociedad.
Costa, a £32 million acquisition from Atletico Madrid in July, gave Jose Mourinho's men the ideal preparation for their Premier League opener at Burnley on Monday with a deserved victory.
Chelsea made the perfect start when Costa opened the scoring in the second minute. The striker was unleashed by a fine Ramires through-ball and made no mistake in dispatching past goalkeeper Enaut Zubikarai from a tight angle.
He then doubled Chelsea's lead five minutes later when he tapped home from close range after Andre Schuerrle's shot crashed off a post and into his team-mate's path.
Costa missed a chance to snatch a hat-trick in the second half while Fernando Torres also fluffed a clear-cut opening.
Thibaut Courtois - largely untroubled for most of the match - had to be alert to deny Chory Castro in the 77th minute.