* Off-key holders still in hunt for third Cup win in a row
* Orient through to fifth round after another upset (updates after later games, adds quotes)
Holders Chelsea needed a late equaliser by Salomon Kalou to snatch a 1-1 draw that kept them in the FA Cup after a Louis Saha header had put Everton on course for a fourth-round upset at Goodison Park on Saturday.
In another of the weekend's five all-Premier League ties Aston Villa beat Blackburn Rovers 3-1 in a repeat result of their third-ound meeting a year ago. All their goals came in the first half from Ciaran Clark, Robert Pires, who won the Cup three times with Arsenal, and Nathan Delfouneso.
Leyton Orient, struggling at the wrong end of League One (third division), pulled off a second successive upset win when, having knocked out Norwich City away from home in the last round, they won 2-1 at Championship (second division) promotion-chasers Swansea.
Manchester United, 11-times winners, visit League One Southampton later on Saturday in a repeat of the 1976 final when then-second division Southampton claimed a shock 1-0 win.
Chelsea, bidding to be the first team to win the FA Cup in three successive seasons since Blackburn Rovers managed it in 1884-86, lacked urgency and looked more like the team who struggled so badly in December than the one who had had won their last two league games.
Everton, who have won one and drawn four of the teams' last five Premier League meetings but did lose to the Londoners in the 2009 final, took control and Petr Cech did well to keep out a header from the dangerous Marouane Fellaini.
Everton broke through after 62 minutes when Saha met a Leighton Baines corner to power a header past Cech.
With youngster Jack Rodwell outclassing Michael Essien in midfield Everton remained on top and Seamus Coleman was twice denied by Cech and then a John Terry block.
Chelsea boss Carlo Ancelotti reacted by sending on Kalou in the 70th minute and five minutes later the Ivorian had equalised when he finished off a swift counter-attack in virtually Chelsea's only chance of the half.
Everton finished strongly but Cech made another great stop in stoppage time to keep out a rising drive by substitute striker Jermaine Beckford.
"Everton put us under pressure and played good football and created chances to score, so the result is good. It was not a good game but in general it was a good performance," Ancelotti told ESPN TV.
"Everton have a special kind of football, play a lot of long balls and they like to fight in the box on set-pieces. But we showed a good attitude and spirit even though we did not play well."
When asked about his club's bid for Liverpool striker Fernando Torres the Italian said: "I don't know, we will have to wait."