But worse was to come at Vicarage Road as the struggling Hornets could afford to miss a first-half penalty twice and still run out comfortable winners.

Solskjaer has managed to ride out the storm during previous poor runs since taking charge in 2018.

But United's latest slide comes after heavy pre-season investment on Cristiano Ronaldo, Jadon Sancho and Raphael Varane that were expected to turn the team into title-winners for the first time since 2013.

Financial results released this week for the first quarter of the season showed United's wage bill has risen 23 per cent.

However, that has not been rewarded on the field as the Red Devils find themselves 12 points adrift of Premier League leaders Chelsea down in seventh and out of the League Cup.

Much more was expected after steady progress during Solskjaer's first two full seasons in charge.

He secured back-to-back top-four finishes in the Premier League for the first time since the club's decline began with Alex Ferguson's retirement as manager in 2013.

However, Solskjaer, who famously scored United's winning goal in the 1999 Champions League final against Bayern Munich, has failed to win a trophy since his return to the club.

His legendary status as a United player meant the 48-year-old retained the support of fans even as results went downhill in recent months.

But even they began to turn on him on Saturday as he was booed while holding his hands up in apology.

"We were outfought," said Solskjaer. "The first half is the worst we've played and it's hard for me to explain why we played the way we did.

"The boys are in a terrible place in their heads now -- we have let ourselves down and the fans down. It's hard to stand here and explain that, but that's football and we have to take the flak for it."

Former Real Madrid boss Zinedine Zidane, Leicester manager Brendan Rodgers and Ajax coach Erik ten Hag are the frontrunners to be Solskjaer's successor. (AFP)