Still, they’re expected to mount a better challenge for top honours in the new season. Yet their summer has thrown up more questions than answers regarding how they’ll go about doing that.
Here’s a look at five issues facing United manager Jose Mourinho heading into the new season.
Underwhelming transfer window
United’s summer began with the signing of Fred, which came with requisite hype – he was the second player, after Alexis Sanchez, to be prised away from the clutches of fellow admirers Manchester City.
However, after the Brazilian failed to play a single minute at the World Cup, the aura around his signing has dissipated – even if that was partly injury-enforced.
Couple that with United’s other transfer business, the addition of 19-year-old right-back Diogo Dalot and Lee Grant as third-choice goalkeeper, and it’s safe to say United fans are underwhelmed by their club’s summer business.
But the news that really sunk United fans was that of Marouane Fellaini signing a contract extension. In one stroke, Fellaini’s decision to stay symbolised the continuation of the functional, uninspiring nature of United’s play under Mourinho, and allowed the manager to conclude his work was done in terms of bolstering his midfield. No Sergej Milinkovic-Savic arrival, or that of anyone else, looks likely now.
Fred: Of the 34 players to have attempted 25+ dribbles in the Champions League this season, Fred has the best dribble success rate (88.5%)— WhoScored.com (@WhoScored) May 24, 2018
For more player stats -- https://t.co/xwZi8mgZ8I pic.twitter.com/bSImm40S4i
Stick or twist with Martial?
The Anthony Martial situation is resulting in two stand-offs. One is between club and player, with Martial adamant about wanting to leave and thus seemingly irked that United can trigger a one-year extension to his contract, which otherwise expires after this season. For United, doing so is a no-brainer – the extension gives them more leverage in transfer negotiations.
But a second stand-off is emerging within the club. Mourinho is apparently ready to let Martial go, as long as it’s not to a Premier League rival. CEO Ed Woodward, on the other hand, doesn’t want to sell the youngster at all. Watching the Frenchman flourish elsewhere would be a huge regret for United.
Meanwhile, Martial will be the team’s starting striker on opening day, with Romelu Lukaku and Marcus Rashford still on post-World Cup holidays. The club are hoping good form and an extended run in the first XI would convince both player and manager that Martial is a part of United’s future.
Anthony Martial scored a goal once every 175.67 minutes in the Premier League in 2017/18; a better rate than any other Man Utd teammate to play at least 700 minutes.— Squawka Football (@Squawka) June 13, 2018
26.67% conversion rate. 🎯 pic.twitter.com/AlxPW5W0Nd
An un-Mourinho defence
United finished with the league’s second-best defensive record, conceding only 28 goals. Yet the defence still seems an area of concern.
Phil Jones had pundits purring at the beginning of last season, as he was hailed as the best English defender around. He ended it by floundering against Eden Hazard in the FA Cup final.
Chris Smalling and Marcos Rojo are inconsistent and mistake-prone, Eric Bailly was strangely discarded in the second half of the campaign and Victor Lindelof’s maiden season at United was spent acclimatising to England.
Mourinho prioritises a solid defence above all else, so expect the Red Devils’ rearguard to be upgraded in the coming weeks, with a big-money move for Leicester City’s England hero Harry Maguire being considered.
Most dribbles completed of defenders in the last two Premier League campaigns:— WhoScored.com (@WhoScored) July 22, 2018
🥇 Harry Maguire -- 80
🥈 Hector Bellerin -- 70
🥉 Antonio Valencia -- 66 pic.twitter.com/u1L5IIE9DD
Style of play
Pre-season is no indicator of a club’s performance, especially with World Cup exertions depleting squads of many first-choice players. It’s no surprise that United haven’t looked at their best without Paul Pogba, Jesse Lingard, Lukaku, and Rashford.
The question is whether they will ever be that side under Mourinho.
United showed flashes of being a juggernaut last season, especially at the beginning when they were nearly matching City goal for goal. As their form began to dip, however, Mourinho’s returned, with the side playing less and less exciting football.
Second place was a worthy achievement but it was never going to satisfy United fans who could see their neighbours conquer the Premier League with a side playing thrilling football.
Mourinho may never match Pep Guardiola in that regard, and if he wins, it won’t matter. But it’ll be heartening for United fans to see the handbrake lifted against the lesser lights of the league, at the very least.
The biggest question on any United fan’s mind at the moment is whether this side is good enough to reign supreme over City and everyone else.
Guardiola’s side are seemingly poised to continue their dominance, Liverpool look a more threatening side than last year, and Tottenham and new-look Chelsea and Arsenal sides should be expected to offer more of a challenge.
At the moment, United seem to be relying on internal development to stave off everyone else, hoping that a newly-crowned world champion Paul Pogba will be an improvement on last year’s version, Sanchez will be fresh after his first full summer in five years, and Lingard and Rashford will have developed even further after their own thrilling World Cup run.
Will that be enough?
While a number of players including – Paul Pogba, Marcus Rashford, Romelu Lukaku were not part of the squad for the pre-season clash, the Premier League outfit were able to field Alexis Sanchez and Anthony Martial.
Speaking after what was an uneventful game between the two sides, Mourinho told MUTV – “We are not a team. We’re a group of players from different teams.”
“Some are first team, some Under-23s, some coming from loans and going on loan, some are younger, Under-18s. We don’t have a team to play much better than we did but [it’s] one more training session.”
Meanwhile, United had an injury concern to deal with as Antonio Valencia had to be taken off quite early.
“He’s injured and I think we need to get used to it,” Mourinho said.
“Last season he was already in this type of situation and this season he will probably have more of that.”
The Portuguese manager was however satisfied by the display of Chilean forward Sanchez who made his first start after joining the squad late in pre-season.
“Good for Alexis.”
“The first time he plays after some individual sessions. He needed this and he made a good effort, a good physical effort, which is important for him in this moment.”
Youngster Andreas Pereira too had a decent game. The 22-year old looks keen to leave a mark before the main season gets underway, and Mourinho looks content with the midfielder’s performances so far.
“Andreas is playing okay. In the first match, he was okay and today too. I think he has to play even more simply than what he’s doing but he has the personality to want the ball and to organise. I’m happy.”
— Manchester United (@ManUtd) July 22, 2018
Ander Herrera has defended Manchester United teammate and fellow Spaniard David de Gea by saying the goalkeeper was only criticised for his World Cup performance because of the world-class status he had earned.
“I don’t care what the critics say,” Herrera said. “He is the best goalkeeper in the world, by far, and he will show it again.
“When you are the best goalkeeper in the world and you don’t make those amazing saves, everyone is going to talk.
“When I don’t play very well, I don’t get that criticism because I am not one of the best in the world, but he is, so it’s normal and he will cope with it.
“He is so strong. I remember when I was in Spain and he signed for the club [in 2011], the first couple of months were hard for him and he became the best goalkeeper in the world in the next four years, so I am very relaxed about him.
“We are very lucky to have him.”
De Gea was criticised after spilling a Cristiano Ronaldo shot during Spain’s 3-3 draw with Portugal during La Roja’s opening World Cup game. That error came after a similar one during a warm-up game against Switzerland.
Herrera has backed United fans to help De Gea recover after his World Cup nightmare.
“They are very loyal. They have already shown that to him and he knows he’s going to get them back.
“We are very relaxed because he is going to show again that he is the best in the world and he will give us again eight or 10 points this season.
“I remember that difficult summer  when everyone was talking about Real Madrid and he played the first game at Old Trafford and everyone was singing his name and he told me: ‘This is amazing, they are the best.'”