Birmingham 0 Chelsea 2
AVB who? Roberto the Cup legend leads Blues revival
Roberto Di Matteo may not be a candidate to replace Andre Villas-Boas on a permanent basis but he has reinforced his status as Chelsea's FA Cup legend.
Di Matteo, for all his self-confidence, is unlikely to become too comfortable in the role despite two goals in six second-half minutes from Juan Mata and Raul Meireles to beat a depleted Birmingham team and advance into the last eight.
The three-year Villas-Boas project lasted less than nine months, so the interim manager will take it one step at a time. Next up are Stoke, on Saturday, then Napoli in the Champions League before the quarter-final at home to Leicester.
Juan-nil: Spain midfielder Mata celebrates after putting Chelsea ahead at St Andrew's
Beat Leicester and it is back to Wembley for the man who scored historic FA Cup final goals for Chelsea as they won the trophy in 1997 and 2000.
The omens are good. When Guus Hiddink took control from Luiz Felipe Scolari, three years ago, his first game was an FA Cup tie at Watford and he went on to win the competition at Wembley.
Scolari banked his pay-off, watched from a distance and still seems bitter about it. If Villas-Boas was looking on, he will have detected slight signs of improvement from the same players who resisted his changes and rebelled against him.
There were few signs of mourning, apart from Meireles, who refused to celebrate his brilliant goal and Di Matteo, his former assistant, who dedicated the win to the manager who departed on Sunday.
'Roman Abramovich, he sacks who he wants,' sang Chelsea supporters with more than a hint of glee. This was their first chance to offer an opinion on the managerial change and the game had barely kicked off when they chanted the name of Jose Mourinho. More than 3,000 fans had travelled and they also made their feelings known that they did not want Rafa Benitez.
Di Matteo made changes. First he changed his tracksuit for a skinny tie and posh overcoat and gave the squad a little shake as he selected his first team since he was sacked by West Bromwich 13 months ago.
There were five changes to the Chelsea team beaten at the Hawthorns on Saturday in what would prove the last game of the Villas-Boas era. On the bench were Frank Lampard and Didier Drogba, although they were apparently assured that this was a decision made with the next two fixtures, and the rest of the season, in mind.
On the touchline: Chelsea caretaker boss Roberto Di Matteo (right) gives his orders
Ashley Cole was injured but John Terry was among the substitutes less than a fortnight after a knee operation which was expected to keep him out for up to eight weeks.
Perhaps more significantly, Di Matteo made a tweak to the usual Chelsea shape. The 4-3-3 became a 4-2-3-1 formation with Meireles and John Mikel Obi deployed as deep midfielders and Mata playing up front, just behind Fernando Torres.
No spring in his step: Chelsea's misfiring striker Fernando Torres did not score yet again
The inability to make Torres function effectively played a part in the downfall of Villas-Boas, who irritated Abramovich by comparing his poor form and fragile confidence to other expensive misfits Andriy Shevchenko and Mateja Kezman.
On his 50th Chelsea appearance, Torres continued to look timid and hesitant at the times when instinct ought to kick in. When a clear chance dropped on his left foot in first-half stoppage time, he screwed it badly wide and after he was tripped for a penalty in the second half and Mata stepped forward to take it, the home crowd chanted: 'We want Torres.'
They need not have worried. Birmingham goalkeeper Colin Doyle saved Mata's penalty, just as he had in the 1-1 draw at Stamford Bridge but, by then, Chelsea were two up and on the way to ending a run of three successive away defeats.
Chris Hughton's side, playing their 47th game of the season, had resisted well in the first half. Chelsea were vulnerable when defending against counter-attacks and set-pieces and Petr Cech was forced to scramble and turn a header from Nikola Zigic over, five minutes before the interval.
Packs a punch: Chelsea goalkeeper Petr Cech stretches to repel a Birmingham cross
Zigic had stitches in a cut above his left eye after taking a boot in the face from David Luiz but his effort from Jordon Mutch's cross nearly embarrassed the expensive central defensive partnership.
Late on, a dreadful clearance from Gary Cahill gave a chance to Marlon King but Cech saved and Mutch tore clean through only to blaze over.
Problems remain for Chelsea despite the departure of Villas-Boas but they were good enough to seize control after the break and it was Mata who found the breakthrough, nine minutes into the second half.
Ramires stole the ball from Mutch on the right and Salomon Kalou, bright on his first start since October, fought down his cross in the goalmouth. It spilled to Mata who adjusted his feet and poked a shot inside the far post. The tension eased away.
Back on the bench: John Terry was in Chelsea's squad despite his recent knee surgery
Mata headed wide from a Branislav Ivanovic cross and, on the hour, Meireles pounced to score a wonderful second. Again it came from a move down the right and Ramires nursed a short pass into his path and the Portuguese midfielder fired a right-footer into the top corner.
He refused to celebrate, pushing his team-mates away angrily but the overwhelming vibe from Chelsea as they tossed shirts to the fans at the end was one of relief. They are back on the Wembley trail and free from the stifling attention to detail of AVB.
Chelsea fans would have been surprised and delighted to see their captain sitting on the bench so soon after his knee injury.
The 50th appearance in a Chelsea shirt for the £50m man. In that time he has averaged just 2.5 goals per manager.
The 3,000 travelling supporters made it clear in explicit terms that they do not want the Spaniard at Chelsea.