Story of the game
On an incredibly cold night at Old Trafford, the opening 25 minutes failed to warm the place up. The most clear-cut chance came through Victor Lindelof when his header was tipped onto the post following a finger-tip save by Lukasz Fabianski.
Mason Greenwood enjoyed the first half as he was the only spark in a dull contest. For West Ham, attacking opportunities were scarce but they were organised at the back.
Marcus Rashford had an opportunity to score on his 250th appearance for United and probably should have done. Early in the second half, Fabianski came to the rescue again for the Hammers as he stood tall and Rashford struck the ball straight at him.
The Hammers enjoyed a period of domination in the second half. Moyes' side pumped balls into the box for Tomas Soucek - who has been excellent aerially this season.
Soucek caused another problem in the box when he challenged Lindelof to a header, Aaron Wan-Bissaka attempted to clear the ball but nearly sent it over Dean Henderson's head and into his own goal. The United keeper tipped it over for a corner.
Bruno Fernandes came on late in the second half and United found their rhythm. It took the Portuguese maestro 30 seconds to ping a ball out wide for Greenwood to chase - something that Donny van de Beek failed to do in 73 minutes.
Another tedious 45 minutes meant the match finished 0-0 and the teams went to extra-time.
The substitute, McTominay, took matters into his own hands and toe-poked the ball home from a Rashford lay-off to give United a 1-0 lead in the seventh minute of extra-time.
The clock kept on ticking and West Ham ran out of time to conjure up a comeback. United were victorious and qualified for the quarter-finals of the cup.
Rashford and Martial both make 250th appearance for the club
The pair of forwards set high standards for themselves as they burst on the scene both under the age of 20. Rashford - who came from Fletcher Moss junior football club - has since gone on to score 83 goals for the club, surpassing Eric Cantona.
Rashford came into a poor United side and has done remarkably well to put up the numbers he has done considering some of the 'deadwood' he has had to play alongside. The young Englishman has already had to play under three managers and three dissimilar styles of play.
On February 25, Rashford will celebrate five years since he bagged a brace against Midtjylland in the Europa League. From ending Martin Demichelis' career at the Etihad to snatching two winners at the Parc des Princes, Rashford has had a promising start to his expected long and successful United career.
As for Martial, he joined United for a British record fee for a teenager. He signed from AS Monaco for £36 million and many had their doubts, or as the United fans sing 'the English press said he had no chance'.
Martial's career at United has been a rollercoaster of emotions. He was the favoured number nine at the club until Zlatan Ibrahimovic arrived in Manchester under Jose Mourinho and he is now second to Edinson Cavani who Solskjaer signed in October 2020.
Martial is a player that thrives on self-confidence and he does not hide his emotions when upset or frustrated. Under Solskjaer, United saw the very best of Martial in the 2019/20 campaign where he enjoyed his best season statistically. The Frenchman scored a career-high of 23 goals in all competitions and contributed 12 assists.
This season, Rashford and Martial are yet to be as clinical as they are best known for. Rashford's creative play has improved as he already has 11 assists, but Martial is struggling and his facial expressions say it all.