Mark Hughes' Stoke City future hangs in the balance after the Potters crashed out of the FA Cup with a 2-1 third-round defeat at the hands of fourth-tier Coventry City.
A break from their Premier League problems - Stoke sitting third bottom after a disappointing festive period - failed to materialise at the Ricoh Arena as Hughes' men were beaten by a Jack Grimmer screamer.
Stoke's exit was the biggest upset with Bournemouth earning a replay with Wigan Athletic thanks to Steve Cook's stoppage-time equaliser in their 2-2 draw at the Vitality Stadium.
After trailing at half-time against Burnley, Manchester City had Sergio Aguero to thank for their 4-1 home victory, while 10-man Swansea City will need a replay to get past Wolves.
There were no such problems for Watford, Huddersfield Town, West Brom, Newcastle United and Southampton, though, as they all booked fourth-round spots.
THINGS GET GRIMMER FOR HUGHES
Hughes was already under pressure at the bet365 Stadium after one league win in seven, and he got no reprieve in the cup as Stoke fell to the in-form Sky Blues.
Jordan Willis grabbed the first with his first of the season in all competitions, but after Hughes' half-time team talk Charlie Adam appeared to spark a revival.
His penalty just before the hour restored parity, but it was the League Two side who got the winner, Grimmer unleashing a superb strike beyond Jack Butland.
SUPER SERGIO RESCUES CITY
200 - Mark Hughes oversaw his 200th game in charge of Stoke (W71 D48 L81), losing six of the last eight (W1 D1). Strain. pic.twitter.com/CqKxeqmUUk-- OptaJoe (@OptaJoe) January 6, 2018
Manchester City's quadruple hopes remain intact despite their early scare against Burnley, Ashley Barnes firing Sean Dyche's men into a surprise lead.
Back came City, though, with Aguero scoring twice in as many minutes to put his side ahead just before the hour.
KING KUN pic.twitter.com/gP64pmPORc-- Manchester City (@ManCity) January 6, 2018
Burnley's resolve was broken and the hosts added gloss to the result thanks to Leroy Sane and Bernardo Silva late on.
NO VARDY, NO PARTY
Jamie Vardy's return to Fleetwood Town lacked the fairytale ending as he missed the clash through injury, and without him Leicester City could only draw 0-0.
Claude Puel's side failed to have a shot on target in the 90 minutes, leaving Fleetwood goalkeeper Chris Neal with a clean sheet and a year's supply of pizza from a club sponsor for keeping the Foxes out.
A replay is the last thing Leicester needed, but it could have been a lot worse had Ashley Hunter's late deflected strike not struck the woodwork.
Aston Villa's recent revival under Steve Bruce - which included a 5-0 thrashing of Bristol City - came to a juddering halt as they were beaten 3-1 at home by Peterborough United.
Fellow promotion candidates Cardiff City were also frustrated as Mansfield Town earned a replay after a 0-0 stalemate, while Sunderland's problems continued as goals from Rudy Gestede and Martin Braithwaite gave Middlesbrough a 2-0 win.
Meanwhile, MK Dons eliminated QPR at Loftus Road and Yeovil Town - fourth bottom in League Two - shocked Bradford City.