Marcus Rashford and Rasmus Hojlund had given the visitors a dream start with two goals inside the first 20 minutes.

But a double from Samu Omorodion, after Pepe brought Porto back into the game, had the English giants heading for defeat.

United then had captain Bruno Fernandes sent off for the second consecutive game, but the 10 men salvaged a point when Maguire headed in a corner.

Ten Hag's men have now begun their Europa League campaign with two draws after being held at home by FC Twente last week.

And the manner of their capitulation after a fast start will do little to ease the pressure on their manager ahead of Sunday's daunting Premier League trip to Aston Villa.

The former Ajax boss responded to the 3-0 humiliation by Tottenham last time out by making four changes.

Hojlund came in for his first start of the season alongside Casemiro, Christian Eriksen and Amad Diallo.

Ten Hag could not have wished for a better start, even if Porto were architects of their own downfall.

Rashford has shown flashes of a return to his best form after a disappointing 2023/24 campaign and opened the scoring with his fourth goal of the season.

The England international skipped between two Porto defenders before firing in a shot that Portugal number one Diogo Costa should have kept out.

Rashford then turned creator for the second as his pass fed Hojlund, who again beat Costa at his near post with a powerful strike.

But just as Ten Hag was beginning to breathe a sigh of relief on the touchline, United's two-goal advantage was wiped out in seven minutes.

Pepe reduced the arrears by stooping to head in the rebound after Andre Onana had produced heroics to prevent Noussair Mazraoui's header finding his own net.

Omorodian could have been lining up for Chelsea in the Premier League had the Spaniard not failed a medical that led to his move from Atletico Madrid collapsing.

But he has seven goals in his first six games for Porto and brought the home side level with a towering header.

Worse was to come for the visitors and their beleaguered boss after the break.

Rashford's promising display was cut short at half-time as he was replaced by Alejandro Garnacho.

Onana produced a fine save inside the first two minutes of the second half to deny Francisco Moura at his near post.

But that warning shot was not heeded as the United defence was shredded once more by a sprightly Porto counter-attack on 50 minutes.

Pepe sprinted down the left beyond Lisandro Martinez and his low cross was blasted high past Onana by Omorodian, who had escaped the attentions of Matthijs de Ligt.

Fernandes then picked up a second yellow card on his return to Portugal.

But it was the man who Ten Hag stripped of the captaincy that could have saved his job.

Maguire rose highest to power home Eriksen's corner in the 91st minute to salvage a point.