Manchester United are one of the big spenders during the transfer window with a net spend of over €200M but particular attention zooms in on Real Madrid veteran midfielder Casemiro who joined Old Trafford.
Casemiro became the latest player to move from Real Madrid to Manchester United in a deal worth £70m in the summer to join the list of players who have played for both clubs.
Let's take a look at five players who have donned both clubs' jerseys.
Cristiano Ronaldo left Manchester United to join Real Madrid in 2009 in a world record deal of £80m after hugely successful years at Old Trafford.
He won numerous titles in England and scores of individual awards, including the prestigious Ballon d'Or award in 2008, after leading Manchester United to a Premier League and Champions League double.
Ronaldo joined Real Madrid in 2009 as part of another Galactico era alongside Ricardo Kaka and Xabi Alonso.
He went on to score 451 goals in 438 matches in all competitions to become their all-time top scorer.
Ronaldo won four Champions League titles, three Club World Cups, three Uefa Super Cups, two Laliga titles, two Copa del Rey and two Spanish Super Cups.
He won numerous major individual awards at Real Madrid, including four Ballon d'Or awards, two FIFA best awards and many more.
Ronaldo left Real Madrid in 2018 to join Juventus.
England's Golden Boy, David Beckham, enjoyed a successful time at Old Trafford, winning six Premier League titles, two FA Cups and one Uefa Champions League trophy before leaving to join Real Madrid in 2003.
Beckham was a runner-up in the 1999 Ballon d'Or award behind Barcelona star Rivaldo.
He also finished as runner-up twice in the FIFA World Player of the year award in 1999 and 2001.
He made a total of 394 appearances for Manchester United, scoring 85 goals.
Beckham joined Real Madrid in 2003 for €37 million after clashing with Manchester United manager Sir Alex Ferguson.
Beckham's time at Real Madrid was not as successful compared to his time in England, he made a total of 159 appearances for Real Madrid, scoring 20 goals and recording 51 assists.
He won only two trophies at Real Madrid- one Laliga title and Spanish Super Cup.
In 2007, he left Real Madrid to sign a five-year deal with MLS side LA Galaxy.
Ruud Van Nistelrooy is one of those players who can boast of being successful at Manchester United and Real Madrid, he scored a combined 214 goals for the two teams.
He joined Manchester United from PSV in 2001 in a club-record deal worth £18.5 million.
The Dutch striker scored 150 goals in 219 appearances for Manchester United in all competitions, winning one Premier League title, one FA Cup, one League Cup and the Community Shield.
He won 20 individual awards at Old Trafford, including Premier League player of the season, Pichichi and the Uefa Champions League top scorer award three times.
He joined Real Madrid in 2006 in a deal worth €14 million.
Van Nistelrooy had a successful time at the Santiago Bernabeu.
He played 94 matches for Real Madrid and scored 64 goals.
Van Nistelrooy won two Laliga titles and one Spanish Super Cup in Spain before leaving Real Madrid in 2010 to join Hamburg.
Argentine winger Angel Di Maria joined Manchester United from Real Madrid in 2014 for a club-record deal of £59.7 million, and he was quickly handed the famous number 7 shirt.
Unfortunately, he failed to live up to expectations at Old Trafford.
At Real Madrid, Di Maria shone like a star scoring 36 goals and recording 85 assists in 190 appearances.
He won one Champions League trophy, one UEFA Super Cup, one La Liga title, two Copa del Rey trophies, and one Spanish Super Cup trophy.
He left Real Madrid in 2014 to team up with Manchester United, and he only lasted one season before he was shipped out on loan to PSG.
Di Maria made 32 appearances for Manchester United, scoring four goals and recording 10 assists.
Javier Hernandez, popularly known as Chicharito, joined Real Madrid on loan from Manchester United in 2014.
At Manchester United, he made over 150 appearances scoring 59 goals, he also won two Premier League titles, and he was part of the Manchester United team that lost to Barcelona in the 2011 Champions League final.
He joined Real Madrid on loan in 2014, scoring 9 goals in 33 appearances for the club.
Raphael Varane joined Manchester United in 2021 after spending 10 years at Real Madrid.
The French defender enjoyed a hugely successful time at the Santiago Bernabeu.
Varane scored 17 goals in 360 matches for Real Madrid, winning 18 trophies, including four Uefa Champions League trophies and three European Super Cups, among many others.
He teamed up with Manchester United in 2021 and endured a topsy-turvy first season which was blighted with injuries and inconsistency.
In his second season, he has started the club's last four Premier League games under Erik Ten Hag.
Casemiro is one of the best defensive midfielders in the world, and he was a key member of the Real Madrid team that won the Champions League trophy three times in a row from 2016-2018.
He made 331 appearances for Real Madrid, scoring 31 goals, winning five European Cups, three Club World Cups, three UEFA Super Cups, three Laliga titles, one Copa del Rey trophy and three Spanish Super Cups.
He joined Manchester United in the summer from Real Madrid for £70m, he made his debut against Southampton.
Casemiro has made three appearances for Manchester United so far this season in the Premier League.