Big names like Wesley Sneijder, Luka Modric and Nani could all be on the move soon.
Even for Premier League Champion Manchester United, the transfer window is a busy time.
While Sir Alex Ferguson will want to keep the core of his team intact, the Red Devils cannot become complacent if they hope to repeat as Premier League victors.
Here are 15 Manchester United transfer rumors.
The 21-year-old midfielder played a key role in the effort to keep Wigan from relegation toward the end of last year.
Cleverley has yet to suit up for the Red Devils in a competitive match, having spent time at Leicester City and Watford on loans before Wigan.
His performance last season may have raised him a couple spots in the Man-U pecking order, but the U-21 English international still is very unlikely to crack the starting 11.
Wigan boss Roberto Martinez hopes that if Cleverley decides to go out on another loan he will choose the Latics over other suitors.
Man-U has already accepted a £5 million bid for the midfielder from Sunderland, so Newcastle would have to match or exceed the bid and then negotiate personal terms with Gibson himself if they are to pull off this daring move.
This rumor, courtesy of the Sunday Mirror, seems too fantastic—it could easily be a ploy by Newcastle to rattle their rivals.
The Wanderers have expressed interest in bringing Jonny Evans to Wolverhampton.
Evans will see his playing time disappear next season with the arrival of Phil Jones.
The 22-year-old defender signed a four-year deal with United last year. If he is available, it will likely be for a loan.
Wolverhampton manager Mick McCarthy pursued Evans two years ago, but was unsuccessful in landing him.
According to the Daily Star, United had planned to make an £18 million bid for Daniele De Rossi, but their cross-town rivals are prepared to offer nearly double (£35 million).
Sir Alex Ferguson has long been interested in the Italian international, and would be thrilled to plug De Rossi into a midfield that needs some help.
The star midfielder has become a lightning rod for criticism on an underperforming AS Roma squad and has long been linked with moves out of the Italian capital.
De Rossi has been a Roma fan since his childhood days, and could easily decide he'd prefer to weather the storm and stay on his current club anyway.
Veteran defender John O'Shea could possibly be headed to Liverpool this summer.
The Irish international's departure from Old Trafford is a near certainty given Sir Alex Ferguson's desire to cut payroll without making drastic changes.
Liverpool have unsuccessfully attempted to sign left backs Gael Clichy and Jose Enrique, but desperately need to strengthen their defensive line if they hope to compete for the Premier League title.
The 30-year-old Irishman can play right, center or left back, as well as a serviceable defensive midfield. He is valued at approximately £6 million.
O'Shea has also been linked to Sunderland.
David De Gea has signed a five-year contract to complete an £18million move from Atletico Madrid.
The Spaniard has some very big shoes to fill, as he will be replacing United legend Edwin van der Sar.
But De Gea is one of the best young prospects in the world, and is certainly up to the task. He has held his own in La Liga against much older and experienced keepers.
De Gea was a part of the Spanish U-21 team that won the European Championships last week.
United target Alexis Sanchez is reportedly about to sign with Barcelona.
The 22-year-old midfielder caught the eye of many European clubs, including Chelsea, Man City and Man-U.
But the Chilean has long been known to favor Barcelona, and appears set to play at Camp Nou next season.
Of interest: according to TalkSport, Barcelona will attempt a shock move for United's own Nani should the Sanchez deal somehow fall through.
Juventus are in need of a midfielder, as the futures of Mohamed Sissoko and Felipe Melo are uncertain. The Torino-based side apparently identified the 30-year-old Park as a solid replacement.
The South Korean international just announced his desire to play out his contract with the Red Devils earlier this week.
"I have nothing to say about any transfer rumours - I just want to stay at Manchester United," said Park when questioned about a possible move to Serie A.
Park's status in Manchester had been up in the air for some time. Rumors looked to be settling down until Juventus stirred the pot again.
Promising Spanish midfielder Thiago Alcantara has signed a two-year extension with Barcelona, effectively ending speculation of a move to the Premier League.
United, Chelsea and Arsenal were all known suitors of the young star, but his performance at the European Under 21 Championships, including a ridiculous 45-yard free kick, convinced Barcelona to lock him up through 2015.
Sir Alex Ferguson made a £15 million offer for Alcantara last week, but the Catalans were hesitant to sell to a Champions League rival.
Alcantara's availability was widely believed to be tied to Barcelona's pursuit of Cesc Fabregas, whose presence would render the youngster superfluous.
Barcelona have opted not to make the same mistake they made with Fabregas, and are electing to keep the budding star rather than selling him and attempting to buy him back several years later.
Valencia will reportedly offer £14 million for United's star striker Dimitar Berbatov.
The Bulgarian striker's future has been in serious doubt since the end of last season, which featured him on the bench in some key games, most notably the Champions League final.
United's supposed interest in Napoli striker Edinson Cavani is further proof that Berbatov has fallen out of favor with Ferguson.
Paris St. Germain are another club linked to Berbatov, but they have not formally made a bid for the striker.
Napoli has announced that star striker Edinson Cavani is worth €100m (£89m).
The Red Devils were considering a £25million bid for the Uruguayan international possibly to replace Dimitar Berbatov. Arsenal, Tottenham, Manchester City and Real Madrid are also believed to have interest.
"They would have to revoke my president's licence if I sold Cavani for less than €100m," said Napoli president De Laurentiis. "He is worth much more than what those in England have been writing."
Clearly Napoli and United differ on their opinions of Cavani's value. But £64 million is a pretty ridiculous margin, and promises to feature some pretty serious haggling.
Per the Daily Mail, Bayern Munich are preparing a £20 million bid for Nani.
The Portuguese winger had a fantastic season for the Red Devils last year, but the signing of Ashley Young has put his playing time in jeopardy.
Bayern Munich already has two quality wingers in Arjen Robben and Franck Ribéry. However, the two are oft injured, and are creeping up there in age.
Skysports News reports that the 24-year-old Nani is unfazed by the Young signing, and will fight hard for his spot on the starting 11.
"Of course I have to welcome everyone they sign," said Nani. "It is good for the team, we want more (players) to help us to win trophies."
Manchester United will offer £20 to acquire Samir Nasri from ancient rival Arsenal.
The £20 bid could be too much for Arsene Wenger to refuse, as Nasri is entering the last year of his contract and is refusing to sign any new deals.
Wenger has made it clear Nasri will not leave on a free transfer. It follows logically that if Arsenal cannot ink the French midfielder to an extension, they will be forced to sell him.
Arsenal is in danger of losing its two best midfielders in one week, as Barcelona has upped their offer for Cesc Fabregas to £34 million.
Samir Nasri would fill the void left by retired Paul Scholes as a playmaking midfielder. That they are stealing him from the Gunners would only sweeten the deal for United.
ESPN reports that Manchester United are considering challenging Chelsea for the services of Tottenham star Luka Modric.
The Spurs recently rejected a £22 million bid from Chelsea, and insist that Modric is not for sale.
Sir Alex Ferguson openly admires Modric, and is determined to bring him to Old Trafford.
According to the Daily Star, United will offer Spurs around £18 million plus Premier League top-scorer Dimitar Berbatov, whose departure from Old Trafford has been much discussed.
Modric is currently valued at around £30 million.
Manchester United are prepared to break the bank in an attempt to land Inter playmaker Wesley Sneijder.
Sir Alex Ferguson desperately wants a dynamic force in the midfield to replace retired Paul Scholes.
The sticking point with the Dutch star, valued at around £30 million, was his outrageous wage requests.
After Chelsea and Manchester United balked at his £200k-per-week demands, Sneijder said he'd be happy to remain on a successful Inter team.
Sneijder has played his cards well, as United appear on the verge of making him the offer he wanted in the first place.