Manchester United lost the chance to move back to the top of the English Premier League table after they suffered a shock 2-1 home loss against Sheffield United on Wednesday night.
Kean Bryan and Oliver Burke scored for the Blades, with captain Harry Maguire grabbing the consolation for the hosts.
Coach Ole Gunnar Solskjaer made six changes to his side from the team that played Liverpool in the FA Cup on Sunday, with the likes of Axel Tuanzebe and Nemanja Matic starting.
The Blades sat deep in the opening minutes, with the hosts looking the likeliest to score.
It however was the visitors who came closest to scoring the opener in the 17th minute, but David De Gea made a wonderful stop to deny Billy Sharp after beating the offside trap.
The Blades threatened again in the 21st minute, but Tuanzebe was in the right place to clear the danger.
They were not to be denied though in the 23rd minute as Fleck, who up until that time was the best player on the pitch, whipped in a brilliant ball from the corner right onto De Gea.
The Spaniard didn't have any conviction though and Bryan had the easy task of flicking a header into the net for the opener.
United thought they had pulled level on the half-hour mark, but Anthony Martial's goal was chalked off after Maguire was adjudged to have nudged Aaron Ramsdale.
The second period was largely dominated by United, even though the first real chance on goal came after the opening quarter.
Marcus Rashford swerved in a nicely-hit free-kick from the edge of the box, but it went straight at Ramsdale, who got his body behind the save.
United then got another free-kick, with the resulting effort from Fernandes going behind for a corner.
It's through the corner that Maguire rose highest to head home unchallenged for the equalizer.
It only took the visitors 10 minutes to restore their lead, and it came in a rather comical manner.
United failed to clear their lines, allowing Sheffield to pop it around the box, with Burke managing to find an effort that deflected off Tuanzebe and past De Gea for a 2-1 lead.
There were no more goals as United succumbed to yet another home loss, which might have huge implications in the title race.
For Sheffield, the win gives them hope in their race to scale up from the relegation zone.