Even if the German does complete a blockbuster move to Old Trafford, he won't be the only high-profile signing, so we've generated a list of 20 midfield targets David Moyes should be running the rule over.
Got a name to add? Slam it in the comments below!
The German midfielder wants to be paid in the same bracket as Bastian Schweinsteiger at Bayern Munich, and if the club don't meet his demands, someone else will.
His astonishing showing against Arsenal only enhanced his reputation.
The Daily Star believe Ilkay Gundogan is a £25 million target for Manchester United this summer.
While he would indeed be a perfect signing given his elite talent levels, they'd need to give him the most thorough medical examination in the history of football before stamping the deal.
He's had a spinal issue all season long.
The Croatian has been one of the top three La Liga midfielders this season and should be an attractive proposition for Manchester United.
He's hard-working, energetic, controls a system and has a rasping long shot.
With Sidney Sam arriving at Schalke this summer for a bargain €2.5 million fee, it'd be worth checking in on how Jefferson Farfan feels about his future with the Royal Blues.
If he's unsure, given Sam plays the exact position he does, he's worth a punt; the Peruvian is quick, strong and experienced on the UEFA Champions League stage.
An obvious upgrade over Antonio Valencia.
Koke would have been mad to leave Atletico Madrid for Manchester United this January, but the summer may see a change in how the two clubs are viewed.
If Los Colchoneros can keep up this stunning run of form, then perhaps it's a project worth continuing with, but no one could blame Koke if he felt the club had hit its ceiling.
Atleti are prone to a sale, too.
Borja Valero is as classy as they come.
He's a midfield maestro, strolling around in first gear and dominating the centre of the pitch. His ability to control games, dictate the tempo and bring every teammate into proceedings is a valuable commodity in the modern game.
Fiorentina look unlikely to reach the UEFA Champions League, and if that stops Valero breaching the Spanish national squad, he may look for a new venue to showcase his talents.
Heung Min Son won't come as cheap as Bayer Leverkusen snagged him for last summer, but he'd be well worth the plunge for a fee of around £15 million.
He's a clever winger who dips inside and hangs off the shoulder of defences, and if Manchester United have a genuine wide man opposite him, he can work magic in space.
The ultimate right-wing upgrade this summer is Juan Guillermo Cuadrado.
The Colombian's talents will be on show at the 2014 FIFA World Cup in Brazil, and those who haven't seen him before are in for a real treat.
He's obscenely quick, takes players on and can cross superbly without hesitation. A hefty £20 million should do it.
Rafa Benitez has taken it slow in introducing the Brazilian to life in Naples, but long-term this could cause an issue for one of the Swiss trio currently in situ.
Blerim Dzemaili probably won't interest David Moyes, but should Valon Behrami or Gokhan Inler hit the market, he should be first in the queue holding a large cheque.
Internazionale tried desperately to get rid of Fredy Guarin this winter but failed.
With any luck, a strong showing with Colombia in the 2014 FIFA World Cup can turn some heads, though, and if he shows a better attitude, top clubs will be falling over themselves to open negotiations with the Nerazzurri.
He's powerful, fast, dominant and has a frecracker of a long shot.
Not Benat, not Ander Herrera: Ander Iturraspe has been Athletic Bilbao's best central midfielder this season.
His consistency has reached new levels, and he's growing into his role as the prime defensive midfielder in the side. He used to look a little lumbering and slow as a youngster, but he's matured quickly into a stellar presence on the field.
Manchester United tried to nab Thiago Alcantara last summer and failed.
He does have a brother, Rafinha Alcantara, though, and there'd be no shame in signing the slightly lesser of the two supremely talented siblings.
He's currently on loan at Celta Vigo and impressing greatly, and the Express even believe United have made contact with parent club Barcelona over a potential transfer.
Dusan Tadic is the most creative player in the Eredivisie and can play in an assortment of different positions in midfield.
He's perhaps at his best in a narrower role so he can see more of the ball, and most expect the Serbian to earn a big move away from Holland this summer.
His versatility and wizard-like feet make him a strong option for David Moyes.
Axel Witsel would cost a bomb, but he'd be worth every penny.
He is the first name on the team sheet for Belgium manager Marc Wilmots for a very good reason: He's reliable, clean, effective and physically unparalleled.
The Zenit man is one of the most graceful enforcers you'll ever see and stands a mightily underrated asset.
A surprise selection, perhaps, to those of you who don't follow the Italian national team or Serie A, but Emanuele Giaccherini is an extremely good player who simply hasn't settled into a tumultuous Sunderland setup.
He's a star for the Azzurri and Cesare Prandelli is happy to deploy him in an assortment of positions, with his versatility and hard work two key factors working in his favour.
He'd be a nuts-and-bolts player, nothing too flashy, but for around £8 million, he represents a very interesting option.
The moment Memphis Depay learns to be less wasteful with good goalscoring positions, he's a lock for a big transfer away from PSV Eindhoven.
He's an intriguing prospect full of dynamism, speed, positivity and strong dribbling ability, so some excellent coaching could have him producing on a wide scale within six months.
If Tottenham Hotspur really don't want Lewis Holtby, Manchester United should deliver an enquiry to see how much he'd cost.
The German is not the world-beater many hoped he would be after arriving from Schalke last January, but he's an extremely reliable, serviceable player who can play deep in midfield, as a No. 10 or out wide.
He's excelling for Fulham on loan.
If David Moyes is looking for a seasoned professional who's peaked and ready to win, Selcuk Inan could be the perfect fit.
The Galatasaray central midfielder is revered in Turkey as a passing maestro, but he hasn't quite hit the heights of last season where he was mixing it with the very best.
If a change of scenery comes calling, Inan should be a major target.
Christoph Kramer will run relentlessly until the final whistle...and then probably run some more.
If work ethic is a key factor going into the summer, Kramer should interest David Moyes after the young midfielder displaced Havard Nordtveit in the Borussia Monchengladbach setup.
He's not flashy, but he's a more effective body than some of the current crop.
Depending on how highly Miralem Pjanic values UEFA Champions League football, the Roma star could look to cash in on a superlative season in Serie A by landing a huge pay rise.
A £25 million-plus bid will tempt the Giallorossi to sell in all likelihood, and the Bosnia & Herzegovina international can double his money at Old Trafford should he elect to sign.
Based on form this season, he's worth top dollar.