It has been relatively quiet at Old Trafford so far this summer, but that is soon expected to change with David Moyes having targeted a number of potential signings.
Here are five players that have been identified to improve the Manchester United squad ahead of the 2013/14 season.
At the age of 22, the Italian-born Spaniard has played for the Barcelona first-team 68 times. He is a very skilful, creative midfield player, exactly what United are lacking.
The Under-21 captain is available at around £15m as he failed to appear in enough matches last season, which activated a release-clause in his contract.
Barcelona are keen to hold onto the player, and very recently it has emerged that former manager Pep Guardiola is interested in taking him to Bayern Munich which could thwart Moyes' advances.
Baines would be a great signing for United, he is a fantastic full-back and would fit perfectly into the team.
He had a great campaign last season under Moyes and would provide healthy competition for the ageing captain Patrice Evra.
Having already had a bid rejected for the defender, Moyes is expected to up his offer, with Everton reportedly valuing him at £20m.
The 6ft Polish striker's goal-scoring record is up there with the worlds best.
Last season he scored a mouth-watering 36 goals in 48 appearances in all competitions, capping off an amazing season by becoming the first person in Champions League history to score four goals in a single game, following his sides 4-1 demolition of Real Madrid in the first leg of their semi-final.
Lewandowski has been linked with a move to United for a few years now, but according to reports it now seems more likely that he will join current European champions Bayern Munich next season on a free transfer.
The Belgian midfielder has been one of the best midfielders in the Premier League over the last two seasons.
Standing at 6ft4in, he is a powerful, fast and creative player. He would be an ideal signing for the Premier League champions.
Moyes brought Fellaini to Everton in 2008 for £15m from Standard Liege. He has proved to be worth every penny and has stood out as their best player.
Recent reports have linked him with a move to Arsenal rather than United, but if Moyes misses out on Thiago Alcantra to Bayern Munich then returning to his old club and taking Fellaini would be a fantastic alternative.
Ronaldo, along with Messi, is one of the best players in world football.
He has scored a staggering 146 goals in only 135 appearances for the Spanish giants.
After leaving Manchester United for a world record fee things off the pitch haven't always been smooth for the Portugese international.
Rumours persist of his unhappiness in Madrid and that would put the Red Devils in pole position if he ever wanted to leave the Spanish club.
Write for GiveMeSport! Sign-up to the GMS Writing Academy here: http://bit.ly/12evFlH
DISCLAIMER: This article has been written by a member of the GiveMeSport Writing Academy and does not represent the views of GiveMeSport.com or SportsNewMedia. The views and opinions expressed are solely that of the author credited at the top of this article. GiveMeSport.com and SportsNewMedia do not take any responsibility for the content of its contributors.