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And in a BBC Match of the Day vote 77.2% agreed with him.
"Chelsea are by far the best team in England at the minute. They are 2-0 up at home against little Bradford," said the 39-year-old, who won the Cup with Liverpool in 2001.
"For me this is the biggest shock."
Ex-Tottenham midfielder Jermaine Jenas added: "This is what we all love about the FA Cup. The shock exit.
"The thought that Bradford could go to Stamford Bridge and win was not on anybody's mind. The fact that they are 2-0 down away from home and can go on and have the spirit to win is amazing."
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Chelsea 2-4 Bradford - No fluke
The League One side's victory over the Premier League leaders at Stamford Bridge left Blues boss Jose Mourinho to admit he was "ashamed" of the FA Cup exit.
Here is how the rest of the football world reacted:
Former England winger Chris Waddle, BBC Radio 5 live:
"It's an incredible day. That is an amazing result.
"It doesn't matter what side Chelsea put out, they should beat Bradford City. That's no disrespect to Bradford - give them credit, they've stuck at it, they've had a big following down there and they've enjoyed their day."
Former Chelsea midfielder Nigel Spackman, BBC Radio 5 live:
"I think Bradford they deserved to win the cup tie. It was an amazing cup tie. Chelsea put all the big guns on but weren't able to break Bradford down.
"In the second half, Bradford were absolutely magnificent. I think Chelsea were a little bit complacent at 2-0 up. At that stage, it looked as though the match was over. It just shows you what FA Cup football is all about. You keep going until the whistle."
QPR goalkeeper Robert Green on Final Score:
"Did the changes to their starting line-up make a difference? You'd think so. But you'd say they could make 40 changes with the squad they've got, with the players out on loan. They can make as many changes as they want, they have enough quality in every team they'd ever put out to win that game."
BBC football analyst Steve Claridge on BBC Radio 5 live:
"There was absolutely no fluke about that. Bradford fully deserved it. Some of the quality of their play was brilliant."
Man City 0-2 Middlesbrough - Lack of respect?
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City rode their luck against Football League opposition Sheffield Wednesday in the last round where they came from behind to secure a late 2-1 win, but that luck ran out against Aitor Karanka's side, who are second in the Championship.
Waddle:
"I think Manchester City have only got themselves to blame. Flying back the night before the game, landing at 7pm, after playing a midweek friendly - what are they thinking about? I just can't believe it.
"If you don't treat the FA Cup with respect, you get your fingers burned."
Jenas:
"This is a Boro team that has conceded six goals in 15 games. They are well drilled and know their roles.
"When needed, bodies were put on the line. But they were never worried, they knew their jobs and made blocks and City had no answers. An all-round brilliant performance."
Green:
"Has the trip to Abu Dhabi had an effect on City? You'd probably say not, but I think if manager Manuel Pellegrini had been given a choice, knowing the owners of Manchester City, he wouldn't have gone.
"I think it was something that's probably been forced on them. If he gets a phone call this evening, the first thing he'll probably say is: 'Well, I didn't want to go there.'
"But if you look at the squad, and the quality in it, they should be breaking teams down."
Tottenham 1-2 Leicester
Southampton 2-3 Crystal Palace
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Chelsea's 4-2 home defeat by League One side Bradford was the biggest FA Cup shock of all time, says former Liverpool striker Robbie Fowler.