Dimitar Berbatov scored what proved to be the winning goal against his former club as Manchester United beat Tottenham Hotspur 2-1 in a pulsating FA Cup fourth round tie at Old Trafford on Saturday.
Berbatov, who left Spurs for United in August, beat the offside trap to put the home side ahead two minutes after a deflected long range shot from Paul Scholes had cancelled out Roman Pavlyuchenko's fifth minute opener for Tottenham.
Swansea City had earlier scored the day's biggest upset when they knocked out holders Portsmouth with a deserved 2-0 fourth-round win at Fratton Park.
Portsmouth, who beat Cardiff City in the Cup final in May, had no answers against another Welsh side, Championship (second division) Swansea winning with goals from Nathan Dyer, on loan from Portsmouth's arch-rivals Southampton, and a penalty from Jason Scotland.
Portsmouth manager Tony Adams, who took over from Cup-winning coach Harry Redknapp when he moved to Spurs in October, could not hide his disappointment after his side had been outplayed.
"It is not nice going out, full stop," Adams said.
"It doesn't matter whether you're the holders. When you are out-fought and outplayed for 45 minutes then you are always likely to be dumped out of the Cup."
There was little room for FA Cup romance elsewhere with none of the other unfancied teams managing upset victories.
Minor League Kettering Town came close to achieving a draw against Premier League Fulham before Andrew Johnson and Bobby Zamora scored late goals to give the visitors a 4-2 win.
Doncaster Rovers, struggling at the wrong end of the Championship, played above themselves to hold high-flying Premier League visitors Aston Villa to a goalless draw.
Burnley of the Championship also did well to draw 2-2 at West Bromwich Albion with a late equaliser from Martin Paterson.
Burnley, who were knocked out of the League Cup in the semi-finals by Tottenham Hotspur on Wednesday, still have the chance of adding another Premier League scalp to their belts this season by taking West Brom back to Turf Moor for a replay.
They have already seen off Fulham, Arsenal and Chelsea in the League Cup this season.
Minor League Torquay United held Championship side Coventry City until the 87th minute before the visitors scored the only goal.
Apart from Portsmouth, none of the Premier League teams involved in the afternoon's matches lost with West Ham United seeing off League One (third division) Hartlepool United's challenge with a 2-0 win at Victoria Park.
Chelsea, though, made hard work of beating Championship side Ipswich 3-1 at Stamford Bridge with Michael Ballack scoring twice and Frank Lampard adding the third with a stunning 35-metre freekick in the closing stages.
Ipswich caught Chelsea napping after 34 minutes when Alex Bruce equalised before the home side forced their way back.
Sunderland and Blackburn Rovers drew 0-0 in the only all-Premier League match of the afternoon and Manchester United were playing Tottenham Hotspur later in another top-flight clash (1715 GMT).
Hull City reached the fifth round for the first time in 20 years with a 2-0 win over League One (third division) Millwall and Middlesbrough scored a 2-1 win at Championship leaders Wolverhampton Wanderers with Marvin Emnes scoring the late winner for the visitors.