Mourinho's tinkerings meant a first start of the season for midfielder Scott McTominay, playing on the right of a three-man defence, while Anthony Martial played instead of the dropped Alexis Sanchez. On this evidence, more changes may be needed when United take on Valencia in the Champions League on Tuesday.
Leaders Barcelona and Real Madrid were held to draws while Sevilla made up ground on the top two and Alaves slipped after a promising start. Here are five talking points from the weekend's La Liga action.
Quaison fires Sweden to extra-time World Cup playoff win over Czechs
Messi, who has struggled for form in recent weeks due to a niggling injury, looked on a mission to grab the winner and after twice coming close he completed his treble to put Barca ahead in the 85th minute, reacting quickly to a poor Sevilla clearance to dink the ball over goalkeeper Tomas Vaclik.
Bayern Munich coach Pep Guardiola says there is no way of stopping Barcelona's Lionel Messi in his present form ahead of their Champions League semi-final clash on Wednesday.
Real Madrid defender Raphael Varane made up for the absence of Sergio Ramos by scoring one goal and making another to help his side to a hard-fought 3-0 win at Getafe. La Liga leaders Barcelona were held to a 2-2 draw at struggling Espanyol on Saturday as China striker Wu Lei came off the bench to grab a late equaliser in a pulsating city derby.
Barca made a slow start to the campaign under their new coach but after beating Paris Saint Germain in the quarter-finals they are on course to repeat the treble success.
News of all that's transpired on and off the football field
Included in Barcelona squad to face Dortmund
Barcelona manager Luis Enrique believes his team deserves to win "the best league in Europe" as they aim to clinch La Liga in a potentially thrilling climax to the Spanish season on Saturday.
Neymar's double helped Barcelona cruise to a 5-0 victory in the first leg of their King's Cup last 16 tie against Elche.
Real Madrid beat Leganes 4-2 on Wednesday despite resting key players including Cristiano Ronaldo and Gareth Bale as goals from Alvaro Morata and James Rodriguez helped them stay top of La Liga after Barcelona cruised to a 3-0 win over Sevilla.
- 'The match epitomised our season really' - 'Today we were the better side in the first half but you can't concede the goals we did'
Barcelona coach Luis Enrique is leaving the Spanish La Liga champions at the end of the season when his contract expires after three trophy-laden seasons at the club.
Cristiano Ronaldo, fired up by rival Lionel Messi's midweek hat-trick for Barcelona, struck four goals in 26 second-half minutes as Real Madrid crushed Celta Vigo 7-1 at the Bernabeu on Saturday.
Images and a round-up of all the World Cup qualifiers played across continents on Tuesday.
News of all that's transpired on and off the football field.
Manchester City must put a potentially ruinous fortnight behind them as they seek to reboot their faltering season with a big performance in their Champions League last-16, first leg trip to Dynamo Kiev on Wednesday.
Lionel Messi scored his 12th league goal of the season but Barcelona had to rely on exceptional saves from Marc-Andre ter Stegen as they rode their luck to win 2-0 at Athletic Bilbao on Saturday and stay four points clear at the top of La Liga.
Barcelona's Lionel Messi and Luis Suarez secured victory over nine-man Atletico Madrid in La Liga's top of the table clash, while Juventus won a 12th straight Serie A game to stay hot on the heels of leaders Napoli.
A summary of sports events and sports persons, who made news on Saturday
The injury list in the La Liga keeps growing as the season progresses and this time Lionel Messi and Gareth Bale are the unfortunate victims...
Barcelona's Lionel Messi is the best player ever, Bayern coach Pep Guardiola said.
The clinical Argentine Messi now has 11 goals in his last five games in all competitions and with record signing Ousmane Dembele injured and Luis Suarez rested, he put on a sensational show at Camp Nou to extend Barcelona's La Liga lead.
An insatiable Lionel Messi hit a hat-trick as Barcelona hammered Espanyol 5-0 in a local derby on Saturday to make it three wins from three and take full advantage after Liga champions Real Madrid were held to a 1-1 draw at home to Levante.
Images from Wednesday's action in the UEFA Champions League.
News of all that's transpired on and off the football field
Argentina and Brazil both lost their opening World Cup qualifiers on Thursday as the South American campaign for Russia 2018 started in unexpected fashion.
As Barcelona prepare to welcome back Pep Guardiola to the Nou Camp for Wednesday's Champions League game against Manchester City, check out how the club has evolved since the visionary coach departed in 2012.
Lionel Messi had to wait 12 years and endure a goal drought of eight games against Chelsea but he finally broke his duck in Tuesday's 1-1 Champions League last 16, first leg draw.
This and more from the happenings in the world of football
In other matches, super-sub Messi helped Barca romp past Atletico
Promoted Alaves dealt champions Barcelona a shock 2-1 defeat at the Nou Camp on Saturday while Cristiano Ronaldo returned from injury to help Real Madrid thrash Osasuna 5-2 and go two points clear at the top of La Liga. With Lionel Messi, Luis Suarez and Andres Iniesta on the bench, Barcelona went behind to the visitors in the 39th minute before Frenchman Jeremy Mathieu equalised in the 46th. Ibai Gomez then scored the winner in the 64th.
Liverpool captain Steven Gerrard says Sunday's defeat to Arsenal in the FA Cup will not halt his team's momentum as they head into the crucial final stretch of the season.
Champions Barcelona came through a gruelling La Liga test at a rainswept San Mames on Sunday, beating Athletic Bilbao 1-0 thanks to Ivan Rakitic's first-half header.
Manchester United kept up the positive momentum of their pre-season tour with a 3-1 victory over Barcelona in the International Champions Cup on Saturday in Santa Clara, California.
Liverpool manager Brendan Rodgers was an immensely proud but competitive dad at Anfield on Sunday as his Premier League side overcame the FA Cup challenge of his son's third tier Oldham Athletic.
Images from football matches played across Europe.
Cristiano Ronaldo scored his 400th goal for Real Madrid as Zinedine Zidane's side closed in on a first La Liga title since 2012, easing to a 4-1 win over Sevilla on Sunday while Neymar hit a hat-trick for Barcelona, who thrashed Las Palmas 4-1.
Another English football legend, Frank Lampard bid goodbye with a goal for Manchester City on final day of the season
