Erik ten Hag continues to fight for his job as Red Devils manager after a dire start to the season for the club, which has seen them win just three of their first nine games of the campaign.
The Dutchman was hoping that European action would provide some relief from Premier League struggles on Thursday as United took on Porto, but things went from bad to worse in that fixture too and they needed a late Harry Maguire goal to salvage a point.
After the visitors had raced into a 2-0 lead in the first half, Porto hit back with a quickfire double and former Chelsea target Samuel Omorodion scored his second after 50 minutes to swing the game in the hosts' favour.
Old Trafford regular Ferguson wasn't in Portugal to watch the game, however, as he was spotted by television cameras sat at Ibrox to watch Philippe Clement's side in action instead.
Ferguson donned a blue shirt and tie with a blazer as he was all smiles in the stands, though things didn't go as well for Rangers on the pitch.
They found themselves 4-1 down before the hour mark in the game, with Malick Fofana and Alexandre Lacazette both netting two goals easy to ensure Tom Lawrence's goal was in vein and that was how it finished.
Ferguson, 82, was born in Glasgow and played for Rangers between 1967 and 1969.
He has had to watch United struggle in the years since his retirement, with the club still failing to win the Premier League since he called it a day at the end of the 2012-13 season.
He has been a regular in the stands at Old Trafford since, with David Moyes, Louis van Gaal, Jose Mourinho, Ole Gunnar Solskjaer and Ten Hag all trying and failing.
Ten Hag has been backed to succeed on more than one occasion by the United hierarchy but results have failed to improve since he delivered their worst-ever Premier League finish (eighth) last season.
The Red Devils lost 3-0 against Tottenham last time out, and face Aston Villa in the league this weekend, and their captain, Bruno Fernandes, was sent off again on Thursday in the 3-3 draw.
United, meanwhile, raced into a 2-0 lead before they were pegged back and found themselves trailing
A bombshell report in Italy, meanwhile, has claimed that ex-Juventus boss Massimiliano Allegri has the backing of none other than Ferguson to become a potential replacement for embattled Ten Hag.
The report from Gazzetta dello Sport states that Allegri's 'ability to adapt to the most complex situations in the management of the locker room' is another major bonus in his favour, should Ten Hag be relieved of his duties.
Allegri is a free agent after he was sacked by Juventus just days after he won the Coppa Italia last season.