Hojlund's late effort was a bitter pill for Bournemouth manager Iraola to swallow, particularly as neither he nor his coaches believed Evanilson's red card was deserved.
The loss of a vital two points and the suspension that will rule the Brazilian out until the final game of the season against Leicester - by which time the Cherries might well know their fate - could prevent the campaign delivering the first European place it seemed for so long it would.
It will be little consolation to Iraola and his players to reflect - it is so easy to forget it is only 15 years since Bournemouth were promoted out of the fourth tier of English football, as Doncaster and Port Vale have been this weekend.
Development on the pitch since then has been clear, even given this eventual disappointment.
But now owner Bill Foley has big plans off it as well, with an expansion of the Vitality Stadium to take the capacity up to 20,000 planned within the next couple of years.
Even that would be just over a quarter of the size of Old Trafford. The Cherries matchday income in their recently published accounts to 30 June 2024 was £6.53m compared to United's £137.13m over the same period.
Evidently, Bournemouth have put their spending to better use.
At the back, Dean Huijsen and Milos Kerkez excelled as usual, and Alex Scott kept them ticking over in midfield. Crucially, unlike their opponents, they were equally effective at either end of the pitch.
Kepa's stunning reaction save to deny Alejandro Garnacho an equaliser, after the Argentina international had raced clear on to Bruno Fernandes' cross-field pass was sensational.
But so too was the clinical nature of Semenyo's finish as the visitors failed to clear after Patrick Dorgu had initially been ambushed close to the touchline when United tried to play out from the back and the ball was whipped into the penalty area.
It wasn't quite plain sailing for Bournemouth after that but with a historic first European campaign at stake, they seemed to have the grit and determination to keep United out even when they were left a man down.
Sadly for them, Hojlund had other ideas.