For Chelsea, the Tractor Boys appeared in the nick of time.
Managerless and beleaguered, Ipswich rolled into Stamford Bridge and rolled over, inviting Ancelotti's team to restore some confidence after two rotten months.
Up for the cup: Daniel Sturridge is the toast of his team-mates after doubling FA Cup holders Chelsea's lead against Ipswich
For the Italian on the touchline, it must have felt like summertime again as the sun shone down and seven goals flew in. The expression remained glum but he waved to the fans who sang his name.
Frank Lampard and Daniel Sturridge banged in a couple each, Salomon Kalou and Nicolas Anelka found the target while Ipswich's agony was compounded by an own goal from Carlos Edwards.
Chelsea, unbeaten in the FA Cup for nearly three years, go to Everton in the fourth round.
'We needed this kind of performance,' said Ancelotti. 'The result was good and we did a lot of things well, the strikers are scoring again, but we don't have to be excited. We have to wait before we can say everything is OK. There are still some things we can do better but it was important to play well. Our confidence will improve.'
Net gains: Fulop is forced to look on helplessly as Salomon Kalou scores the opening for Chelsea
MATCH FACTSCHELSEA (4-3-2-1): Cech 6; Bosingwa 6, Ivanovic 6, Terry 6, Van Aanholt 6(Bruma 71, 6); Ramires 8, McEachran8, Lampard 8; Kalou 7 (Kakuta 55, 6),Sturridge 7; Anelka 7. Subs not used: Hilario, Ferreira, Essien, Malouda, Drogba.
IPSWICH (4-4-2): Fulop 5; Peters 5,Brown 5, O'Dea 4, Kennedy 5;Edwards 5, Norris 6, Healy 4, Peters5; Wickham 5 (Priskin 63), Scotland 5(Murray 49). Subs not used: Lee-Barrett, Delaney, Smith, Eastman, Civelli.
Booked: Norris.Man of the match: Frank Lampard.
Ancelotti also pointed out how, for the first 20 minutes, it had seemed destined to be another day of frustration. Sturridge missed good early chances and Troy Brown cleared brilliantly off the line to deny Anelka.
But once Kalou struck from an inch, with a goal resembling David Nugent's for England against Andorra, the pressure dissolved.
Anelka was released by Sturridge after a mistake by Colin Healy only for Marton Fulop to drop a heavy hand on his low shot. The ball bobbled on towards the net and Kalou came crashing in to claim the final touch.
Fulop, who conceded seven playing for Sunderland at Stamford Bridge last January, was beaten again within a minute when Sturridge stole ahead of Darren O'Dea to divert a low Jose Bosingwa cross into the net with a neat backheel.
It was 3-0 at the interval after Edwards glanced a header past his own keeper as he tried to clear Lampard's inswinging free-kick. Anelka slid in the fourth, his first in more than two months, and Sturridge curled his second into the top corner.
It was a personal success for Sturridge on his 40th appearance for the club, a landmark which means another £500,000 will be paid to Manchester City, taking his transfer fee, set by a tribunal, up to £5.5million.
Net gains: Ipswich keeper Fulop is helpless to prevented Carlos Edwards' own goal sail in between the posts
With his £60,000-a-week wages, this means the 21-year-old striker has cost £10m and has nine goals, six of them in the FA Cup against the might of Preston, Watford, Cardiff and Ipswich.
Two came in the Champions League against Slovak champions Zilina and his only Barclays Premier League goal since moving from City was the sixth in a 7-0 thrashing of Stoke. Understandably, Ancelotti resisted the temptation to get carried away and promise him another start against Blackburn on Saturday.
'In the future he will have opportunities,' said the Chelsea boss. 'We have a lot of games coming up. He has to fight with the other strikers.'
In focus: Carlo Ancelotti issues the orders as the Italian hides his happiness during his side's emphatic performance
Having scored 11 goals in their previous 13 games, Chelsea blitzed five in 20 minutes, either side of half-time. Lampard helped himself to the last two and, despite his subdued reaction, Ancelotti can at last consider some of those selection headaches managers apparently crave. Does he recall Drogba or allow Anelka a run as the spearhead, flanking him with the boundless energy of Kalou and the boundless confidence of Sturridge?
Does he keep Josh McEachran and Ramires in his midfield trio with Lampard ahead of an out-of-sorts Michael Essien?
McEachran, at 17, is slightly built but his football is fluent, he has rarely looked out of place this season and he was terrific again. Ramires looks better with every game and threatened to break his Chelsea duck with a 25-yarder.
Super strike: Anelka puts Chelsea four-nil up with a fine finish moments after the re-start
For Ipswich it was painful. Caretaker boss Ian McParland is not expected to survive when Paul Jewell is named manager today. Jewell will arrive with his own backroom team and the task of lifting a dejected camp after Roy Keane's sacking ahead of Wednesday's Carling Cup semi-final against Arsenal.
'I live in the real world,' said McParland. 'I knew what was going to happen. The boys were a bit shell-shocked with the manager going. Even with our strongest team, I knew we could have a struggle down here.'
Ipswich's day was made worse when the coach home broke down.
Seventh heaven: Two-goal hero Frank Lampard celebrates with John Terry and his Chelsea team-mates
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Explore more:People: Frank Lampard, Nicolas Anelka, Roy Keane, Carlos Edwards, Daniel Sturridge, Carlo Ancelotti, Jose Bosingwa, Michael Essien, Paul Jewell, David Nugent Places: Ipswich, Cardiff, Scotland, United Kingdom, Andorra