The cup also represents a final chance for a trophy for Spurs, who are coming into the contest off the back of two frustrating league results against Manchester City and Brighton & Hove Albion.
The win at Dean Court has moved the Red Devils four points clear of third-placed Liverpool, leaving Mourinho's charges in the driving seat for a top-two finish.
The performance at Bournemouth might have some wider political implications too. Mourinho was scathing of his players' commitment after being beaten by the Baggies, and the coach made seven changes for the trip to the south coast last night.
Mourinho posited the game as an opportunity for a number of other players to stake a claim for a place in Saturday's starting XI against Spurs. Most notably, Mourinho retained both Ander Herrera and Paul Pogba, who were criticised against West Brom, but both players responded with decisive showings in the win over Eddie Howe's men.
In the midst of speculation surrounding Pogba's future and his relationship with Mourinho, the Portuguese coach leapt to his midfielder's defence last night too, following criticism from former United midfielder Paul Scholes. Mourinho's protection and subsequent praise of his £90m signing might suggest that Pogba's career at the club could take another narrative turn.
With second place now United's for the taking, the club will move their attentions to the FA Cup on Saturday knowing that the tournament presents their final chance to earn a piece of silverware. To clinch it, they will first have to move beyond Spurs and then beat either Chelsea or Southampton in the final.
United go into the clash having kept a clean sheet in six of their last eight matches in the FA Cup, but will be coming up against a Spurs side that cut through them at will when Tottenham won 2-0 at Wembley in the Premier League earlier in January.
The win over Bournemouth might have tightened the club's grip on second spot, but it will not have done much to alter the mood of frustration that still lingers following the West Brom defeat. Beating Spurs to reach the final of the English showpiece might just hint at something altogether more telling.
Recent form: WWWWLW
Recent form (all competitions): LWWWLW
After another standout season for tactical intrigue and progressive football under Pochettino, his charges are now threatened with ending on a whimper as Spurs head into the final few games of the campaign.
The Lillywhites performed admirably in the Champions League and produced a promising 14-game unbeaten run in the league since the turn of the new year. A draw and a defeat in Tottenham's last two games have, however, just given Chelsea a slight glimmer of hope to challenge for fourth.
Spurs appeared completely out of sorts when they surrendered to City on home soil and that result was followed up, granted with changes, by a lacklustre 1-1 draw away at Brighton on Tuesday.
Tottenham are more than likely to finish fourth and securing Champions League qualification will be a relative success as Pochettino tries to keep his key players together over the summer window, but questions will still be asked as to when their fluidity on the pitch will translate into trophies.
Like United, the FA Cup represents the last route to a piece of silverware and the changes made during Spurs' draw with the Seagulls suggest that Pochettino is putting his focus into securing a spot in the final.
Saturday's Wembley venue is meant to present a neutral ground for both sides, although Spurs have evidently found themselves in comfortable surroundings when playing their league home games at the stadium.
What might benefit Spurs too are the scars potentially left on this United side who were put to the sword by Tottenham at the start of their recent unbeaten run earlier in the year. Tottenham have won 10 league games at Wembley this term, losing only twice at the home of English football.
Tottenham have unquestionably continued to make progress under Pochettino, especially when looking at their showings in Europe, but that will not detract from some onlookers bringing up the perennial bugbear of silverware. Getting past United would offer Spurs the chance to potentially silence some of those critics.
Recent form: WWWWLD
Recent form (all competitions): WWWWLD
Mourinho's seven changes midweek gave a number of players the chance to express themselves. Herrera and Pogba might just have reinstalled the coach's faith in the midfield pair.
Romelu Lukaku started on the bench against the Cherries but he will likely return up top. Nemanja Matic should also come back into the starting XI, although Marouane Fellaini will provide Mourinho with another option in the middle.
Alexis Sanchez was left out on Wednesday and it remains to be seen as to whether the Chile international will return.
As for Spurs, Pochettino also rested a number of players against Brighton. Kieran Trippier is likely to replace Serge Aurier at right-back, but Danny Rose is still struggling for match fitness on the other wing.
Lucas Moura took the place of Erik Lamela, but the Argentine should come back into the team at the weekend if he can hold off competition from Son Heung-min. Eric Dier will provide competition for Victor Wanyama, while Mousa Dembele should take the place of Moussa Sissoko.
Manchester United possible starting lineup:
De Gea; Valencia, Bailly, Smalling, Young; Herrera, Matic, Pogba; Rashford, Lingard, Lukaku
Tottenham Hotspur possible starting lineup:
Lloris; Trippier, Alderweireld, Vertonghen, Davies; Dier, Dembele; Lamela, Alli, Eriksen; Kane
Head To Head
The honours have been even between the teams this term. United beat Spurs 1-0 at home earlier in the season, before Tottenham produced a masterclass to outwit the Red Devils at Wembley in January.
United have had the upper hand when being classed as the 'home' side having won the last four. The Red Devils have also kept clean sheets in all of those matches.
Across the last six meetings, all of which have been in the league, the teams have three victories each. In an unusual quirk of inconsistency, the victories have alternated between the clubs after every meeting.
We say: Manchester United 2-1 Tottenham Hotspur
Contests between these sides have been tough to call in recent years, with both teams proving capable of turning in match-winning displays. The results are split this season between the sides, although Tottenham's January victory was emphatic.
The FA Cup presents a final chance for both managers, who will be desperate to claim silverware this season. Tottenham have proven tried and tested goal-scorers in the cup, bagging at least two goals in 10 of their last 11 matches in the tournament.
Spurs will have to account for United stopper David de Gea, though, who has kept 21 clean sheets in all competitions so far this term, more than he has done in any other season.