In a seismic shock Utd lost 2-1 to leave City top by a point having played a game fewer
Even by the standards of this most strange and unpredictable Premier League season the events of this week have been quite astonishing with first Chelsea sacking club icon Frank Lampard then Manchester United losing to Sheffield United.
Lampard's successor Thomas Tuchel got straight down to business Wednesday, beginning his tenure with a dreary 0-0 draw with Wolverhampton Wanderers in the Stamford Bridge rain.
If the sight of the 47-year old German in the technical area took a little getting used to, then the events happening a little later at Old Trafford seemed hardly possible.
Ole Gunnar Solskjaer's United, enjoying a 13-match unbeaten league run, including 10 wins, looked certain to reclaim top spot from Manchester City against bottom club Sheffield who had only won once all season.
But in a seismic shock they lost 2-1 to leave a rampant City top by a point having played a game fewer.
Substitute Oliver Burke grabbed the 74th-minute winner after Harry Maguire had cancelled out Kean Bryan's first-half opener for the struggling Yorkshire side.
For Sheffield boss Chris Wilder it was a rare night of joy in a miserable campaign, although they still remain 10 points behind 17th-placed Brighton and Hove Albion.
Tuchel's opening game was underwhelming in the extreme with Chelsea racking up nearly 900 passes, but offering little goal threat until late on when Mason Mount, Tammy Abraham and Christian Pulisic, all dropped to the bench, came on.
Man City scored three times in the opening half hour at The Hawthorns as they moved to 41 points from 19 games, one more than Manchester United and significantly seven more than struggling champions LiverpoolSports Tribune on Wednesday, 27 January 2021
Mateo Kovacic fired inches wide for Chelsea while Ben Chilwell fired over from a great opportunity, although at the other end Pedro Neto lobbed a great chance over the bar for Wolves.
Tuchel expressed himself satisfied with what he had seen but now knows the job he has to get eighth-placed Chelsea back into the mix for the top four.
Leicester City missed the chance to join City at the top as they were held 1-1 at Everton.
James Rodriguez gave Everton the lead with a 30th-minute stunner but a dominant Leicester deservedly levelled after the break when Everton keeper Jordan Pickford fumbled a skidding Youri Tielemans shot into the net.
Burnley's revival continued as they twice came from a goal down to beat Aston Villa 3-2 - Chris Wood grabbing a 79th-minute winner at Turf Moor.
Burnley, 15th in the table, moved on to 22 points and Villa dropped to 10th on 29.
The day's other game saw 17th-placed Brighton draw 0-0 with 18th-placed Fulham - the most predictable event of the week so far.
Champions Liverpool travel to Tottenham Hotspur Thursday.