Four of the English Premier League's top six were ousted on a classic FA Cup day, with leader Chelsea squandering a two-goal lead to lose 4-2 to third-tier Bradford at Stamford Bridge in the biggest surprise of them all.
"It was a 'Black Saturday' for the Premier League teams," Chelsea goalkeeper Petr Cech said. "Every year you can see this kind of result in the FA Cup. It's just unfortunate that today, for the first time, I was on the wrong side of this miracle."
A virtually full-strength Man City lost 2-0 to second-tier Middlesbrough at Etihad Stadium, raising questions about the wisdom of the English champions' decision to travel to Abu Dhabi for a five-day warm-weather training camp in the build-up to the game. They only returned late on Friday and the team faded in the second half.
"It's easy to have an excuse," City manager Manuel Pellegrini said, "but I don't think (tiredness) was the case."
Southampton, which is third in the Premier League, twice surrendered the lead to lose 3-2 at home to Crystal Palace, and Tottenham — sixth in the league — conceded an injury-time winner to lose 2-1 to Leicester. They were both all-Premier League games.
Swansea lost 3-1 at second-tier Blackburn in another fourth-round stunner, with the Welsh team finishing the match with nine men after getting players sent off in the early and late minutes. Liverpool was taken to a replay by Bolton after drawing 0-0 with the second-tier side.
The upsets began on Friday when star-studded Manchester United was embarrassingly held 0-0 by fourth-tier Cambridge.
As it stands, only three Premier League teams are assured of being in the fifth round — and none are in the top half of the standings. Arsenal and West Ham can change that when they play lower-league opponents on Sunday.
Chelsea's hopes of an unlikely quadruple — Premier League, FA Cup, League Cup and Champions League — were ended by a team used to stunning the big clubs. Two seasons ago, Bradford beat Arsenal and Aston Villa on the way to the League Cup final, where it lost to Swansea.
Forty-nine places in the English league pyramid separated the teams at kickoff and it showed when Chelsea went 2-0 ahead after 38 minutes through goals by Gary Cahill and Ramires.
However, Bradford pulled a goal back in the 40th and a late rally led to goals in the 75th and 82nd minutes, followed by a clinching fourth in injury time.
In two spells as Chelsea manager, Jose Mourinho had never lost against a lower-division team. It means Chelsea has failed to reach at least the fifth round of the FA Cup for only the second time in 17 seasons.
"We must feel ashamed, me and the players must feel ashamed," said Mourinho, who went into Bradford's dressing room after the match to congratulate every visiting player. "Frustration is not the right word — embarrassed would be more appropriate . It is a disgrace that we were knocked out.
"This is the beauty of football, the beauty of the FA Cup," Mourinho added. "It happens more in the FA Cup than any other country."
City, which is second in the Premier League, needed two late goals to beat Sheffield Wednesday in the third round but didn't escape humiliation against Middlesbrough, which is second in the League Championship.
Bamford put Middlesbrough ahead in the 53rd after a first half dominated by City, whose defensive discipline fell apart after halftime. The visitors hit the post — as did City substitute Frank Lampard — before substitute Kike sealed victory in injury time.
"An unforgettable day for us," said Bamford, who is on loan at the club from Chelsea.
On a day of amazing comebacks, Watford rallied from 2-0 down at halftime to thrash Blackpool 7-2 in a second-tier Championship league match.