Chelsea exploited Manchester City's decision to field a weakened team by romping to a 5-1 win in the FA Cup fifth round on Sunday as they joined London rivals West Ham United and Crystal Palace in the quarter-finals.
Second-half goals by Willian, Gary Cahill, Eden Hazard and Bertrand Traore, after the teams went into the break level at 1-1, underlined Chelsea's dominance over a side keeping their powder dry for Wednesday's Champions League tie at Dinamo Kiev.
City, who play Liverpool in the League Cup final at Wembley next Sunday, have now lost three matches in a row.
Chelsea face a stiffer task in the next round away to Everton who they beat in the 2009 FA Cup final.
Crystal Palace's reward for a 1-0 win at Premier League title-chasers Tottenham Hotspur was a plumb away tie with second-tier Reading who shocked top flight visitors West Bromwich Albion 3-1 on Saturday.
West Ham United will next visit Manchester United or third-tier Shrewsbury Town after crushing Championship side Blackburn Rovers 5-1 away - Dimitri Payet and Emmanuel Emenike scoring two goals apiece as both teams finished with 10 men.
Modest Shrewsbury host Louis van Gaal's United on Monday.
If holders Arsenal beat Hull City in a replay, after being held at home by the Championship leaders on Saturday, they will welcome fellow London side Watford.
Manchester City boss Manuel Pellegrini had threatened to sacrifice the FA Cup by making multiple changes, even saying in midweek he would not buy a ticket if he was City fan.
He was as good as his word with six teenagers starting against Chelsea at Stamford Bridge.
Five players - Manu Garcia, Aleix Garcia, Tosin Adarabiyo, Bersant Celina and David Faupala - made debuts as the likes of Sergio Aguero, Yaya Toure and Raheem Sterling were rested.
Faupala cancelled out Diego Costa's headed opener before halftime but the visitors could not hold out after the break.
Pellegrini had criticised the Cup schedule, which gave City less recovery time for their last 16 first-leg clash in Kiev.
"We were forced to select that team," he told the BBC. "We knew it was a difficult chance to carry on in the FA Cup. We cannot do anything more."
Chelsea's interim manager Guus Hiddink is eyeing a repeat of his feat in 2009 when they won the trophy by beating Everton in the Dutchman's last game in charge in his first caretaker spell.
With the much-maligned Hazard returning to form - crossing for Costa's opener, assisting in Willian's effort and curling in a free kick - Chelsea could even afford a missed Oscar penalty.
"Manchester City made changes but that doesn't make it easy because the youngsters that came in were dangerous," Hiddink told the BBC.
One week after Tottenham won at Manchester City to move up to second in the Premier League, they suffered their first defeat in nine matches to a goal by Palace defender Martin Kelly's on the stroke of halftime at White Hart Lane.
Kelly beat Spurs keeper Michel Vorm with a powerful near-post shot to put Palace in the last eight for the first time since 1995.
West Ham are sniffing a first major trophy since winning the FA Cup in 1980 after recovering from an early jolt when Ben Marshall's low shot put Rovers ahead.
Victor Moses equalised and Payet's delightful free kick put the Hammers ahead at the interval before they raced away.
Payet completed the rout with a fine solo goal after on-loan Nigerian Emenike grabbed a brace.
Blackburn's Chris Taylor was sent off after 55 minutes for a second yellow card while West Ham's Cheikhou Kouyate was red-carded for a trip late on.