Manchester United's defensive struggles continued on Sunday against Tottenham as the Red Devils equalled their worst defeat of the Premier League era with the 6-1 thrashing at Old Trafford.
The hosts actually started brightly in Sunday's clash with Spurs, taking an early lead through a Bruno Fernandes penalty.
United were handed the spot-kick within the opening minute, with Fernandes then scoring the earliest penalty in a Premier League game (01:37) since Manchester City star Sergio Aguero against Newcastle in February 2015 (01:12).
However, from that point forward, the wheels fell off as Tottenham began to run riot in what ended up as a four-goal first half.
Spurs' first goal came in the fourth minute through Tanguy Ndombele before Son Heung-min added a brace with goals in the seventh and 37th minutes.
Sandwiched between Son's goals was a goal from Harry Kane, as United's defence completely collapsed in an embarrassing effort from Ole Gunnar Solskjaer's side.
As a result of Sunday's effort, United have conceded at least two goals in each of their first three league games of a season for the first time since 1972, one of several less-than-spectacular marks achieved by the Red Devils' backline on the day.
The Red Devils picked up a 3-2 win over Brighton last week following a 3-1 loss to Crystal Palace to begin their Premier League campaign.
In addition to matching that 38-year-old mark, United conceded four goals in the first half of a Premier League match for the very first time.
The last time the club had done so was in May 1990, prior to the start of the Premier League.
On that day, United were 4-0 down at the break in an eventual 4-0 loss at Nottingham Forest.
As a result of Sunday's flurry, Tottenham became the first visiting side to score four first-half goals in a league game away at United since Spurs themselves also did so in 1957 in an eventual 4-3 win.
But United's frustrations weren't just limited to defending on Sunday, as Anthony Martial was also sent off for an incident involving Erik Lamela.
The French forward was handed a red card for putting his hands on the face of the Tottenham winger as the two battled ahead of a corner kick.
And Martial's red card against Tottenham within 28 minutes was the earliest ever earned by a United player in the Premier League at Old Trafford.
Worse was to come in the second half as goals from Serge Aurier and a Kane penalty completed the rout on Mourinho's return to the club.
United were previously hammered 6-1 at home by local rivals Manchester City in October 2011, while they have also been beaten 5-0 away by Chelsea and Newcastle in the Premier League era - with those defeats also coming in the month of October.
