The Red Devils have stumbled into the new campaign, with a fortunate home win against Wolves followed by a disappointing drop-off in last weekend’s defeat at Tottenham.
Ten Hag accused some of his players of not doing their jobs in the capital and will have been furious by the meek start on Saturday that allowed Forest to race into a two-goal lead.
Fernandes came under particular criticism after Spurs and led United’s turnaround, scoring the match-winning penalty shortly after drawing the foul that saw Joe Worrall sent off.
It was quite the response to a historically bad start. In-form Taiwo Awoniyi brilliantly put Forest ahead on the break with an 86th second goal swiftly followed by Willy Boly from a free-kick.
Never before had United trailed by two goals inside four minutes of a Premier League match, but they rallied as Christian Eriksen pulled one back from a Marcus Rashford cross.
Casemiro wasted a glorious chance to level but made amends shortly after half-time when turning home at the end of a clever free-kick routine.
Worrall’s dismissal for denying Fernandes a goalscoring opportunity gave United extra pep in their step, with the skipper soon scoring from the winner from the spot after Danilo was adjudged to have brought down Rashford.
Forest were now a man and a goal down, but they continued to push. Onana acrobatically denied Boly but United shut up shop, with players leaving to cheers and anti-Glazer chants.
This was United’s first match since it was agreed that Mason Greenwood will leave Old Trafford, where injuries meant Mason Mount and Luke Shaw were in the directors’ box.