This was an FA Cup tie of tepid entertainment and so there was scant surprise extra-time was required. At the end of 90 minutes Craig Dawson missed a header from a corner that would have sent West Ham through against a disappointing Manchester United. But, then, Scott McTominay, one of Ole Gunnar Solskjær’s five substitutions, took responsibility, hitting home Marcus Rashford’s lay-off for a 97th-minute winner. This was about as good as the contest offered, but after Saïd Benrahma spurned a late chance to take it to penalties United progressed to the quarter-finals, as Solskjær continues his quest to secure a first trophy as United manager. The home side dominated, but they caused only occasional problems, while West Ham did offer flashes of danger when hoping to snatch a smash-and-grab winner. But Solskjær was left content, particularly with his match-winner. “Scott has really developed that part of his game this season,” he said. “We have let him go into the box more often – he is a very good striker of the ball, a clinical finisher.” It was the midfielder’s seventh goal of the season and was required on a night when United might have come unstuck. “Going through is always the main thing in the Cup – and bouncing back after the last kick of the ball the other day [drawing 3-3 with Everton],” said Solskjær. “I’m very pleased with the mentality and attitude.” West Ham found it tricky moving upfield: when striker Andriy Yarmolenko dropped into the centre-circle to collect the ball Nemanja Matic instantly squeezed the forward: a microcosm of the pattern of the match. United showed early on they could move from ponderous in the final third to a higher gear. Anthony Martial raced at goal and as Lukasz Fabianski and Angelo Ogbonna closed in the latter became an unfortunate filling in the sandwich and the centre-back had to be replaced by Issa Diop. Mason Greenwood followed a whirl of stepovers with a cross from his right flank that went straight to Fabianski, but it was noticeable how red shirts flooded the box, including Donny van de Beek who was trying to force himself on the game. The Dutchman was present again when a Matic surge-then-cross claimed a corner. From this Victor Lindelöf’s header was deflected and then turned on to his left post by Fabianski. Next Van de Beek pulled the trigger but West Ham remained on level terms. The visitors did go close via a Jarrod Bowen counterattack but Alex Telles’s impressive speed allowed him to take the ball off the winger’s toes. Towards the end of the half a clash of Martial and Diop’s heads caused a break for treatment but each, thankfully, resumed. The sides had to up the quality in front of the goal. A Marcus Rashford run down a blind alley did not augur well as the second half began, but, as a light snow fell, Ben Johnson, on for Bowen at the break, flitted through with a run that scattered United. Ryan Fredericks was the other interval substitution: he had entered for Diop – as a concussion change – and David Moyes’s fourth one occurred when Mipo Odubeko – once of United – replaced Yarmolenko: his second appearance ended in the disappointment of being taken off for Manuel Lanzini towards the very end. Rashford missed a golden chance when Greenwood’s driven ball landed at his feet via Martial but he could not beat Fabianski, who was proving the busier of the keepers. For West Ham, Declan Rice had been a quiet presence in midfield but he made things happen with a give-and-go that claimed a corner as his team appeared more comfortable with three at the back. If anything United had regressed. There was scant zest about them and when Telles hit a five-yard pass straight out for a throw-in this summed up his team’s torpor. With 18 minutes left of normal time Solskjær had seen enough. Off came the insipid Van de Beek and Matic for Bruno Fernandes and McTominay and the latter did the business. “I’m not going to look back on the goal conceded,” said Moyes. “I’ll look at how we played well.”