Holders Manchester United were dumped out of the English League Cup on Tuesday when they lost 1-0 to second division bottom side Southend United in the fourth round.
Celebrations for Alex Ferguson's 20 years in charge of the Premier League leaders were quickly forgotten when Southend's leading scorer Freddy Eastwood, tracked by several top flight clubs, curled in a 30-metre free kick on 27 minutes.
"I am a Man United fan. We didn't think we were going to beat them...but Cup games are hard and they have found that out tonight," Eastwood told Sky Sports.
Ferguson rested some players but still picked a strong side including striker Wayne Rooney and winger Cristiano Ronaldo. A weakened United team had suffered a scare against third division Crewe in the third round.
United became increasingly desperate but had chances to equalise with midfielder David Jones hitting a post straight after Eastwood's goal and Ronaldo forcing Southend goalkeeper Darryl Flahavan into three superb saves.
The side from a town east of London stood firm, however, with the defence giving Rooney an especially rough time. Southend had not previously won in 12 games but still produced the biggest upset in their history.
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Premier League bottom club Charlton Athletic narrowly avoided another shock by beating third division Chesterfield on penalties after drawing 3-3 after extra time.
Charlton twice came from behind and took the lead through Jimmy Floyd Hasselbaink's second strike on 93 minutes but Chesterfield sent the tie to penalties thanks to Wayne Allison's goal in the last minute of extra time.
Chesterfield had knocked out Premier League Manchester City and West Ham United in previous rounds.
Newcastle United also sneaked through to the quarter-finals after overcoming fellow Premier League strugglers Watford in sudden-death penalties following a 2-2 draw after extra time. Newcastle midfielder Scott Parker had forced penalties by netting on 116 minutes.
Wycombe Wanderers also progressed after beating fellow fourth division club Notts County 1-0 in normal time.
In Wednesday's fourth round matches, Birmingham City host Liverpool, Chelsea entertain Aston Villa, Everton face Arsenal, and Tottenham Hotspur play third division Port Vale.