In some of their darker days under Arsene Wenger, as it became apparent that Arsenal would never become champions again under their greatest manager, they still had the FA Cup. In what threatens to prove their worst league campaign in a quarter of a century, it might yet have the same capacity to offer a silver lining. A winner as captain, Mikel Arteta may yet repeat the feat as manager. “It is a great opportunity to try and win a title and play in Europe,” said Arteta. It will require improvement. But if Arsenal rode their luck to triumph at Bramall Lane, prevail they did. It required a dramatic intervention from the substitute Dani Ceballos, delivering an injury-time decider after Sead Kolasinac, with some lamentable defending, had afforded David McGoldrick an equaliser. It needed Emi Martinez, almost embarrassed when Dean Henderson nearly scored with a goal kick that caught the Yorkshire wind, to make a vital save from Billy Sharp when Sheffield United looked the likeliest winners. It entailed two disallowed goals as the Blades’ season of trouble with technology continued. Ultimately, though, it was Arsenal who advance. It was, their manager felt, a triumph of character. “After conceding so late mentally that reaction is not easy,” added Arteta. United, whose drought stretches back to 1925, were eliminated. Winners 13 times, Arsenal are semi-finalists again. They showed their shortcomings at times, but their biggest buy exerted a decisive impact. If Nicolas Pepe has had too few days to savour since his £72 million (Dh326m) move, this was one. Aided by his prowess from the penalty spot, he contributed 23 goals in his valedictory season at Lille. He scored just his eighth for Arsenal but this offered indications his pace could lead to greater potency in forthcoming years. He plays on the right with an Arjen Robben-esque fondness for cutting inside and shooting with his left foot, which twice could have led to further goals. “I am very excited about what he can bring,” added Arteta. “He has incredible potential. I am so pleased to see his defensive actions and then when the ball he gives us creativity.” That was evident as Pepe formed the central part in the move for the winner. The ball went via one substitute, Eddie Nketiah, to another, Ceballos, via the Ivorian. The Spaniard slotted his shot under Henderson. If United, who were caught on the counter-attack, they had more to regret about the opener. Arsenal were without Pierre-Emerick Aubameyang and Mesut Ozil – one rested, the other officially injured – but neither was needed when United helped them to fashion a breakthrough. They had been virtually flawless at the back until errors abounded in a troubled June: after John Egan’s red card and Enda Stevens’ air-kick at Newcastle came Chris Basham’s decision to clip Alexandre Lacazette’s heels just inside the penalty area. “Rash from Bash,” rued manager Chris Wilder and Pepe defeated Henderson with the resulting spot kick. It spurred Pepe on in search of a second. Henderson denied Pepe in their next duel, tipping a low drive past the post. When the winger met the excellent Kieran Tierney’s low cross, he might have beaten the goalkeeper, but his shot whistled past the far post. Yet United spent much of the game on the front foot. They had two more goals disallowed. This time, at least, there was no crowd to boo when VAR curtailed John Lundstram’s celebrations: he was offside when he applied the finishing touch to Oli McBurnie’s header. McGoldrick, too, had strayed before Egan thought he had levelled. Basham, meanwhile, passed up a shot – or, to be precise, a header – at redemption from Jack Robinson’s cross. “We just need a bit more quality when the bullets are flying about,” added Wilder. But then Arsenal came to their aid. Kolasinac only cleared the ball into the luckless Rob Holding and McGoldrick, the striker who could complete the Premier League season without scoring, hooked in his shot. But even when he did score, it proved in vain. “They had to defend for their lives at times,” said Wilder. “We were the dominant team second half. It was more of a Sheffield United performance from start to finish. That was an uncomfortable afternoon for Arsenal.” But, ultimately, a successful one.