There was a point of this match when Manchester United were threatened with the possibility of their first away defeat to lower-league opposition in this competition since Ron Atkinson took a team to Bournemouth, then of the Third Division, in 1984. On Sunday they were losing, against the team second bottom of the Championship, and in those moments the supporters of Blackburn Rovers were given a fleeting reminder of happier times.

It did not last long, however. The harsh reality for Blackburn, under the ownership of the Venkys, is that they are straying dangerously towards third-tier football next season for the first time since 1980. The protest banners against the club’s absent owners hung from every bridge on the M65 and Zlatan Ibrahimovic’s winning goal arrived at the one side of the stadium, the away end, that was full. Almost a third of the crowd was made up by United’s supporters and, though Blackburn acquitted themselves reasonably well, it would be stretching the truth to say the story of this match – the holders and 12-times winners fighting back from a goal down before a late winner from their new hero – was as exciting as it perhaps sounds. What a sad indictment, too, that a tie of this nature could take place with 8,000 unfilled seats.

José Mourinho’s team did have a nervous 10-minute spell after Danny Graham had given Blackburn a 17th-minute lead but they quickly shook their heads clear and it was no surprise they went on to navigate a route into the quarter-finals once Henrikh Mkhitaryan’s beautifully weighted pass had sent Marcus Rashford running clear to score their equaliser.

Ibrahimovic and Paul Pogba are a pretty useful pair to bring on as second-half substitutes and United’s superiority eventually paid off when those two combined for the game’s decisive moment a quarter of an hour from the end of normal time. Ibrahimovic, with another stylish finish, now has 23 goals in his first six months in English football – or 24 if the Community Shield is counted – and is making a decent case to be considered for the individual awards at the end of the season. His latest contribution also meant United avoided a replay and the complication of another addition to an already cluttered schedule, even if a trip to Chelsea in the next round was not the prize they would have wanted.

Blackburn 1-2 Manchester United | FA Cup highlights

Blackburn also have different priorities, starting against Burton Albion on Friday, but Owen Coyle’s team tried manfully to hold out for a trip to Old Trafford once the game became a story of near-unremitting United pressure in the second half. For a side that has spent the last two months in the Championship’s relegation zone, they also displayed a level of confidence that seemed to surprise their opponents in the opening stages. Blackburn were the better side throughout the first quarter of an hour and took the lead with a lovely goal, Marvin Emnes eluding Marcos Rojo to set up the chance and Graham getting away from the flat-footed Chris Smalling to score on the run with a diagonal shot, left to right, past Sergio Romero, United’s stand-in goalkeeper.

Mourinho had given David de Gea, Antonio Valencia and a few others the weekend off and took a calculated gamble by leaving it until just after the hour before Ibrahimovic and Pogba came on for Jesse Lingard and Anthony Martial. Luke Shaw, an unused substitute, must feel like an increasingly peripheral figure but United’s full-backs, Matteo Darmian and Ashley Young, were among their better performers and their willingness to advance from defence was a prominent feature. Mourinho made a point afterwards of mentioning Young’s contribution.

After a slow start United were jolted into life by the shock of going behind and from that point onwards they passed the ball with more authority. Rashford took his equaliser splendidly, taking the ball past the goalkeeper, Jason Steele, before slipping the ball into an unguarded net, and the pass that preceded it, from the outside of Mkhitaryan’s right boot, was a reminder about the imbalance of talent between the two sides.

The arrival of Ibrahimovic and Pogba was another. Rashford and Mkhitaryan moved into the wide positions, with Ibrahimovic taking up his customary position through the middle, and the changes were made at a point when Blackburn’s early sense of adventure had been replaced by a more conservative desire to remain level and try to catch their opponents on the break.

Even then it would be exaggerating to say United overwhelmed their opponents with wave after wave of attacks. Yet the vast majority of the play was towards the Darwen End, where Blackburn were defending, and there was an air of inevitability about the winning goal. Pogba clipped the pass over the top and Ibrahimovic’s first-time finish, once he had realised he was onside, was another reminder of his uncommon gifts, waiting for the ball to drop, adjusting his body position and expertly placing a low shot into the far corner.