Jesse Lingard suffered one of his lowest moments in a Manchester United shirt during the Red Devils' first Champions League group stage game of the season.
The 28-year-old was brought into the fray just after the 70th minute with the scores level at 1-1, Cristiano Ronaldo putting Ole Gunnar Solskjaer's side in front in the opening exchanges before Moumi Ngamaleu equalised just north of the hour mark.
The game appeared to be fizzling out to a standard 1-1 draw, but disaster struck for Lingard in added time as his stray backpass was latched on to by Young Boys forward Theoson Siebatcheu who duly placed his effort beyond the onrushing David De Gea.
Harry Maguire consoled Jesse Lingard after his costly error (Photo by PETER KLAUNZER/EPA-EFE/REX/Shutterstock (12444270bb)
The moment marked one of the worst substitute appearances in recent United history for Lingard, who had just six touches of the ball in 20 minutes worth of action, completing a feeble one pass in the process, losing possession five times.
Speaking after the game, he said: "Last night hurt. Everytime I pull on the shirt, I hope people understand what it means to me.
"I always go out wanting to do the best for the club, the team and the fans. I'm upset for my part in the defeat. Mistakes happen in football but we pick ourselves up and go again."
This weekend, Lingard - providing he is picked - will take on a few familiar faces at the London Stadium, marking his first return to West Ham since spending the latter half of last term in East London.
During his short stint with the Hammers, Lingard lit up the place, playing so well he actually forced his way back into the international fold as he was named in Gareth Southgate's provisional squad for Euro 2020 before ultimately failing to make the final cut.
Despite Solskjaer clearly being a fan of the player, Lingard - who is some way down the attacking pecking order at Old Trafford, has only made three substitute appearances for United this season, though he did bag a goal in his most recent one at home to Newcastle.
The sight of Lingard warming the bench at Old Trafford is a far cry from last season's Hammers heroics, the England star notching nine goals in 16 appearances for David Moyes' side.
This weekend's clash could have looked so very different for Lingard if he had made his switch to East London permanent in the summer, but United demanded £25m at the very least for the forward, a figure the Hammers were seemingly unwilling to pay.
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Jesse Lingard netted nine goals in 16 appearances for West Ham last season
Those high-up in the West Ham hierarchy made no secret of their desire to bring Lingard back on a permanent basis in the summer, assistant manager Stuart Pearce, speaking at the tail-end of the summer window, told talkSPORT : "We would like him to come and join us. That has been an open secret. He was wonderful last year.
"The ball is in Manchester United's court. He is contracted to them. We would like him with us, there is no doubt about that."
However, a move failed to materialise and Lingard will return to the London Stadium donning a Manchester United shirt, looking to bounce back from Tuesday's nightmare as quickly as possible.