Tottenham's poor form continued as they were held 1-1 at Middlesbrough in the FA Cup third round, while the VAR pitchside screen was finally used on a busy Sunday of action.
Pablo Zabaleta was West Ham's unlikely saviour as they battled past League One Gillingham in the FA Cup third round.
The 34-year-old, only on the field as a substitute after an injury to Ryan Fredericks, scored his first goal in almost three years to break the deadlock midway through the second half.
Then, as Gillingham chased an equaliser, fellow sub Pablo Fornals finished them off with a breakaway goal in stoppage time to seal a 2-0 win.
Gillingham threatened an upset as West Ham failed to get to grips with the surface or their opponents during the first half, but they were a different side in the second to ensure they avoided a giant-killing after defeats to League One sides Wigan, AFC Wimbledon and Oxford in recent years.
- West Ham boss David Moyes has progressed in seven of his last nine FA Cup third round ties as manager, falling short to Swansea in 2013-14 and Burnley in 2016-17.
Curtis Jones' thunderbolt inflicted one of Everton's most humiliating derby defeats as a youthful Liverpool progressed to the fourth round of the FA Cup with a 1-0 victory at Anfield.
Eighteen-year-old Jones settled the third-round tie in Liverpool's favour on 71 minutes with a sensational whipped strike that cannoned in off the underside of the Everton crossbar.
Seven changes on average
Premier League teams made over seven changes to their teams on average as the
FA Cup third round followed a hectic festive programme.
Sheffield United altered all 11 players and Leicester and Southampton 10 apiece as teams averaged 7.2 changes.
With Arsenal still to play, only Everton, Tottenham and West Ham have so far made fewer than five.
Everton had looked set to capitalise on Jurgen Klopp's nine pre-match changes as they peppered the Liverpool goal in the first half and forced three quality saves from goalkeeper Adrian.
But Jones' stunning first goal in senior football saw Everton pay the price for missing a host of chances as the Toffees' wait for a first Anfield win since 1999 continued.
Lucas Moura kept Tottenham in the FA Cup as he prevented a third-round shock at the hands of Sky Bet Championship Middlesbrough.
Boro - managed by Jonathan Woodgate, who headed Spurs to victory in the 2008 League Cup final - took a 50th-minute lead through Ashley Fletcher's sixth goal in 11 games.
But Jose Mourinho's men hit back within 11 minutes when Brazilian Moura headed firmly past Tomas Mejias to secure a 1-1 draw and a place in Monday evening's fourth-round draw.
Tottenham were well worth a replay on the balance of play on a day when the injured Harry Kane's absence blunted their attack, but Boro equally deserved another crack after a spirited display against last season's Champions League finalists.
- Middlesbrough striker Ashley Fletcher has been involved in eight goals in his last 11 appearances in all competitions (six goals, two assists), netting in his last three games.
Wayne Rooney helped Derby cause an upset at Crystal Palace to reach the FA Cup fourth round on an afternoon where the pitchside VAR monitor was used for the first time in England.
Referee Michael Oliver watched a replay of an incident between home captain Luka Milivojevic and Tom Huddlestone and overruled his original decision of a yellow card to send off the Eagles skipper midway through the second half. However, the decision came five minutes after the original decision.
One-time Palace loanee Chris Martin scored the only goal against his former club and it proved enough to dump Roy Hodgson's side out of the competition.
- Crystal Palace suffered their first home defeat in the FA Cup as a top-flight side against a lower league opponent, losing 1-0 to Derby.
Callum Hudson-Odoi fired a confidence-boosting first Chelsea goal in four months as the Blues saw off Nottingham Forest 2-0 at Stamford Bridge.
The 19-year-old England forward drilled home the opener then had a hand in Ross Barkley's facile finish as Frank Lampard's side coasted into the fourth round of the FA Cup.
Forest had a penalty chalked off after a Video Assistant Referee review, and Ryan Yates' header ruled out for offside.
But this still remained a comfortable Chelsea win, and one to leave head coach Lampard eyeing an upturn in home form.
Hudson-Odoi will hope his first Blues goal since the 7-1 Carabao Cup victory over Grimsby on September 25 can propel him back to top form. The teenager found himself clutching his right Achilles after one heavy challenge, however, in a small reminder of his continued drive back from surgery in April.
Hudson-Odoi appeared to suffer no after-effects from the robust tackle, but evidently remains mindful of that Achilles tear that yielded a premature end to last season.
- Chelsea have qualified for the FA Cup fourth round for a 22nd consecutive season, last falling at the third round stage back in the 1997-98 season.
A much-changed Sheffield United side did not repeat the mistakes of last year as they overcame AFC Fylde 2-1.
Chris Wilder, who made 11 changes, saw his team go out of the competition at this stage last season as National League Barnet caused an upset at Bramall Lane.
The Blades hosted opposition from the same division again on Sunday but this time avoided a giant-killing thanks to Callum Robinson's early goal and a Leon Clarke strike on the hour.
However, the lowest-ranked team remaining in the competition made the Premier League club sweat by setting up a tense finale when Jordan Williams pulled a goal back with 12 minutes left.
Jordan Hugill scored twice as QPR thrashed Swansea 5-1 to comfortably secure a place in the FA Cup fourth round.
In-form Bright Osayi-Samuel also netted for Rangers, who are on a roll following the recent 6-1 hammering of Cardiff and were three up by half-time.
Substitute George Byers netted for Swansea in the second half but Lee Wallace's brilliant volley with 14 minutes remaining and an even better strike from Josh Scowen in added time completed the rout.
- QPR have scored 11 goals in just two games in all competitions in 2020 (6-1 v Cardiff, 5-1 v Swansea), the first time they've scored 5+ goals in back to back games since August 1962.
Kenneth Zohore's first-half winner booked West Brom an FA Cup fourth-round spot at the expense of Championship rivals Charlton with a 1-0 success at The Valley.
The Addicks made nine changes, handing debuts to recent loan signing Andre Green, as well as youngsters Abraham Odoh and Aaron Henry. West Brom named a completely different starting XI from the side which drew 1-1 with Championship title rivals Leeds on New Year's Day.
Zohore played a neat one-two with Kyle Edwards before coolly slotting a low shot past Phillips from 10 yards in the first half.
Coventry kept their FA Cup dreams alive as they twice came from behind to draw 2-2 at Bristol Rovers, and stay in the hat for round four.
Rovers, still on the look-out for their first win under new manager Ben Garner, went ahead inside six minutes through Jonson Clarke-Harris' early penalty, but were pegged back when Liam Walsh - on loan from rivals Bristol City - levelled up.
Rovers found themselves back in front less than 60 seconds later but an own goal from Tony Craig eight minutes after half-time ensured the spoils were settled.
- Jonson Clarke-Harris has scored four goals in his last six FA Cup appearances, scoring two for Bristol Rovers and two for Coventry City, against whom he scored today for the Gas.
Northampton Town breezed through to the FA Cup fourth round with victory at Burton Albion.
Nicky Adams gave the visitors the lead (10), which was built upon before the break by Ryan Watson (23) and Charlie Goode (45+1).
Ryan Edwards (45+2) did pull one back on the brink of half time for Burton, before Sam Hoskins regained Northampton's three-goal lead with 20 minutes remaining. Scott Fraser (90+1) got a late consolation for the hosts.
- Northampton Town have reached the FA Cup fourth round for the first time since 2003-04, netting four goals in an away FA Cup game for the first time since November 1990 against Littlehampton Town.
Conor Chaplin's second-half header and a late breakaway from Luke Thomas ensured Championship strugglers Barnsley progressed to the fourth round for the first time in seven years with a 3-1 win at Crewe.
The Yorkshire side were ahead as early as the third minute after a fine piece of finishing from Jacob Brown, but the League Two side levelled though veteran midfielder Paul Green.
Chaplin restored Barnsley's lead (75) with a poacher's finish, stooping to head into the corner after Bambo Diaby headed Alex Mowatt's free-kick back across goal.
Then with Will Jaaskelainen up in the visiting box for a free-kick in stoppage time Kenny Dougall released Thomas, who ran clear to finish into an empty net in stoppage time (90+4).
- Barnsley have reached the FA Cup fourth round for only the third time in the last 21 seasons (also in 2007-08 and 2012-13).