Chelsea put an inexperienced Manchester City side to the sword as they won the FA Cup fifth round tie 5-1 at Stamford Bridge.
Blues head coach Guus Hiddink named a strong starting XI, while Citizens boss Manuel Pellegrini handed full debuts to five players as he looked ahead to the midweek Champions League action.
City youngster David Faupala almost made an instant impact three minutes in as he skipped past a couple of defenders and forced Thibaut Courtois into a decent save at his near post.
Ten minutes later the hosts went even closer to the opening goal, as Pedro exchanged passes with Cesc Fabregas before seeing his lofted effort beat Willy Caballero, only to strike the far post and stay out.
Midway through the first half Fabregas smacked in a 25-yard left-footer which arrowed straight at the waiting Caballero and ten minutes before the break the Blues hit the front, as Eden Hazard found space on the left side of the box and his cross picked out Costa to head home with ease.
However, the lead lasted just two minutes before Kelechi Iheanacho found space to play the ball across the face of goal from the right and Faupala bundled it home from close range.
Caballero then kept his side level with a superb close-range block from Pedro five minutes before the interval.
However, he was helpless soon after the restart as the outstanding Willian led a quick counter and took a return pass from Hazard to bury a low, right-foot shot into the far corner of the net.
It was soon 3-1 to the hosts as Fernando’s attempted clearance fell to Gary Cahill and his right-foot effort proved too strong for Caballero, who could have done better.
Midway through the second half Chelsea stretched their lead further, as Hazard won a free-kick 20 yards from goal and then stepped up to curl the resulting free-kick into the corner of the net, with Caballero moving the wrong way.
City almost endured more misery 15 minutes from time when Martin Demichelis was penalised for a foul on substitute Bertrand Traore, but Caballero dived to his right to turn Oscar’s spot-kick away.
Traore struck a post himself as the hosts continued to dominate in the closing stages and the same player added a late fifth as his flicked header from an Oscar cross dropped just inside the far post.