For West Ham’s second string, barring a shock defeat this could hardly have been a more uncomfortable ride. With the captain, Jarrod Bowen, among the clutch of regulars given a breather, it was Crysencio Summerville, a late substitute Nuno Espírito Santo would have rather kept fresh, who spared embarrassment at Burton Albion and helped them into the FA Cup fifth round. Four years ago at Kidderminster in this competition it was Declan Rice who came on to save their skin and it was a similar story here, Summerville’s extra-time strike ultimately preventing penalties.

West Ham squeezed through, Freddie Potts’s red card 11 minutes into extra time for crunching into Julian Larsson ensuring a nervy finale. A couple of nearly-moments may linger; in the final seconds, at which point these teams had been slogging it out for 133 minutes, the substitute Kain Adom saw an effort repelled by Alphonse Areola and Kegs Chauke, another sub, skittled the rebound into the side-netting to gasps.

Quick GuideFA Cup roundup: Saints strike late; Norwich beat BaggiesShow

James Bree scored an extra-time winner to fire Southampton to a 2-1 FA Cup victory at home to their Championship rivals Leicester. Cyle Larin’s penalty in first-half stoppage time put Saints on course for round five but Oliver Skipp’s acrobatic equaliser early in the second half made it 1-1 at the end of normal time. Still, Southampton prevailed against the Foxes for the second time in five days, after Tuesday’s 4-3 away win from 3-0 down at half-time. To make matters worse for Leicester, Blackburn’s victory at QPR dropped City into the relegation zone.

Norwich booked their place in the fifth round as two late goals earned them a 3-1 win over West Brom at Carrow Road. With the game delicately poised at 1-1, after Josh Maja cancelled out Paris Maghoma’s opener, the substitute Ben Chrisene produced a cracking finish to put the Canaries ahead with eight minutes of normal time remaining. The January signing Mo Toure then put the icing on the cake in stoppage time by adding his fifth goal in three games to leave Eric Ramsey still looking for his first win after seven matches in charge of Albion. PA Media

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In the first half the hosts had a penalty appeal waved away when the stand-in West Ham captain, Konstantinos Mavropanos, barged Jake Beesley in the box and in the second half of extra time the Burton striker failed to arrange his feet after reading an inviting cross.

For Gary Bowyer, Burton’s colourful head coach who was wearing boxing gloves when he greeted his squad in the dressing room, a nod to the sporting theme his team adopted through this Cup run, they almost landed a knockout blow. “It was some effort but we couldn’t quite capitalise in key moments – we had to make those count,” said Bowyer, frustrated at the manner of the winning goal. “We had shown the boys what he [Summerville] is capable of doing and he did exactly that.”

Filling his players with belief was Bowyer’s primary objective, empowering them to bridge the 47-place gap between the sides and register their names in history, reaching the last 16 of the competition for the first time. Burton made it to the Carabao Cup semi-finals under Nigel Clough seven years ago, when the goalkeeper Brad Collins, on loan then from Chelsea and now from Coventry, endured a draining night picking the ball out of his net as Manchester City killed the tie with a 9-0 first-leg victory. John Brayford, part of Bowyer’s coaching staff, was in defence that day.

There was a different energy to this game, however, and these opponents were devoid of quality until Nuno introduced Summerville and Valentin Castellanos on 82 minutes. Kick-off was delayed as a hole in Areola’s net was patched up in front of the visiting West Ham fans, who sang against the club’s chair, David Sullivan and vice-chair, Karren Brady. The message also rained down from a few thousand feet, a plane flying over the Pirelli Stadium trailing a banner against the hierarchy.

Tempers flare between Burton and West Ham after Freddie Potts’s red card. Photograph: Mike Egerton/PA

West Ham treated the first half like an inconvenience, Mohamadou Kanté’s skied shot that easily cleared the West Stand terrace symptomatic of a dire display.

Mavropanos was the only survivor from the side that would have beaten Manchester United on Tuesday but for Benjamin Sesko’s 96th-minute equaliser and the debutant Keiber Lamadrid was among those who struggled. It was Adama Traoré, on his first start, who exhibited West Ham’s first flash of Premier League quality nine minutes into the second half, pressing pause and then speeding past Toby Sibbick before sending a dangerous ball into the six-yard box. The ball eluded Callum Wilson and just as Ollie Scarles attacked the cross, Kyran Lofthouse intervened to take it off his toes.

West Ham improved – albeit it was a low bar – against a side who will, like West Ham, reimmerse themselves in a relegation battle next week. Mavropanos soared high to direct a header at Collins and a few minutes later the Greece defender skewed wide. Wilson sent a first-time shot at goal from a tight angle but there was little evidence to suggest this game would finish in regular time.

Both teams struggled to create clear chances, prompting the in-form Summerville to take matters into his own hands four minutes into extra time. The winger darted inside from the left flank and drifted unopposed towards the edge of the box, dispatching a curled shot at goal that looped past Collins via a deflection.

Given the paucity of openings, that, surely, was that? Potts’s red card plunged West Ham into trouble, Jack Armer placing a shot wide before Burton threw bodies forward. Nuno called for Axel Disasi and Malick Diouf to see out the game. It was ugly but West Ham got the job done. “We achieved what we came here to do,” Nuno said.