5 Bruno Fernandes (Sporting CP to Man Utd, £68m)

United had been after Fernandes for a while, but pulled out of a deal in the summer of 2019 after they didn't like how much Sporting wanted for him. But with Ole Gunnar Solskjaer's team struggling and miles off the pace of the top four, they eventually caved into the Portuguese club's demands at the end of January, and boy were they glad they did.

Fernandes has given the Red Devils a new lease of life, and Solskjaer's team stayed unbeaten from the day he signed until the last day of the season. The Portuguese's eight goals and seven assists across 14 matches helped United get third in the Premier League on the final day, as well as helping them reach the semi-finals of the FA Cup and the Europa League.

He was even more dominant in his second season, scoring 28 goals and setting up 17 more in all competitions. Now in his sixth season at Old Trafford, he's got an impressive record of 85 goals and 76 assists in 260 appearances. Fernandes might not be everyone's cup of tea, but he's still United's most influential player and a firm favourite among the fans, who know just how important he is to their team.

4 Andy Cole (Newcastle to Man Utd, £7m)

Cole was the Premier League's hottest young striker when the Red Devils made Newcastle an offer they couldn't refuse in January 1995, sending winger Keith Gillespie the other way as part of the deal. The £7m fee made Cole the most expensive English player ever at the time, and it put a lot of pressure on him. He scored loads of goals in his first season, but also missed some easy chances as United just missed out on the title to Blackburn Rovers and lost the FA Cup final to Everton.

But he soon made up for it by firing United to five Premier League titles, two FA Cups and the Champions League, scoring 121 goals in the process. He was never happier than when he was playing up front alongside close friend Dwight Yorke, who was by far the best strike partner he had. By the time he left Old Trafford, that record transfer fee looked like a steal.

3 Luis Suarez (Ajax to Liverpool, £23m)

Suarez was one of the stars of the 2010 World Cup after helping Uruguay reach the semi-finals, but he already had a reputation for being a bit of a bad boy. He had used his hands to stop Ghana from scoring a goal in the quarter-final, which didn't go down well. No one made a serious bid for him though, and he stayed at Ajax, but soon found himself in more trouble after biting PSV midfielder Otman Bakkal and getting banned for seven matches.

But Liverpool weren't put off by his track record of controversy and signed him for £23m just four days before the transfer window closed. Suarez had a slow start, scoring only four league goals over the rest of the season, but he eventually found his feet and proved to be an absolute bargain. He scored 82 goals in three-and-a-half seasons and took Liverpool to the brink of the title in 2013-14, sobbing uncontrollably when it slipped away at Selhurst Park.

But his time at Anfield was also marked by huge controversy, receiving a 10-match ban for biting Branislav Ivanovic in 2013 and an eight-game ban after being found guilty by the FA of using racist language towards Patrice Evra.

He was still a Liverpool player when he got his third bite on the pitch, after he bit Giorgio Chiellini during the 2014 World Cup, but he was soon bought by Barcelona for £75m, which was triple the amount Liverpool had paid for him three years earlier.

2 Nemanja Vidic (Spartak Moscow to Man Utd, £7m)

When the Serbian first arrived at Old Trafford, he was pretty much an unknown. No one could have predicted that he would inspire United to win five Premier League titles and reach three Champions League finals, and that he would lift the European Cup in 2008.

Vidic and Rio Ferdinand were an unstoppable centre-back partnership, the perfect foundation for Sir Alex Ferguson's last great team. His fierce and uncompromising style of play made him the perfect partner for the calm and collected Ferdinand, who focused on building from the back while his partner dealt with snuffing out any danger.

Vidic was a massive hit with the fans, who loved his full-blooded style of defending, and he became United's captain when Gary Neville retired in 2011. Since he left in 2014, the team's defence has never been quite the same.

1 Virgil van Dijk (Southampton to Liverpool, £75m)

Liverpool had been after Van Dijk for ages and had planned to sign him in the summer of 2017, so much so that Jurgen Klopp had even arranged a private meeting with the defender in a hotel in Blackpool to tempt him to swap Southampton for Merseyside. That meeting got Southampton's back up and led to them upping their asking price for Van Dijk, crushing his hopes of moving in the summer.

Liverpool had to wait until the end of the year, and finally agreed to pay £75m ($94m) for the Dutchman in late December, when the transfer window opened. At the time, it set a world record as the most expensive defender ever bought, and it led to some people accusing Klopp of hypocrisy after he had complained about the fee Manchester United paid for Paul Pogba 18 months earlier. But, unlike with Pogba, Van Dijk proved to be worth every penny.

He was the missing piece in the puzzle for Klopp, and his signing made their defence much stronger. This helped them reach the Champions League final just four months later, and then win Europe's biggest prize in 2019. He was also a massive part of their first league title in 30 years, and when he got a serious knee injury early in the next season, Liverpool basically fell apart without him. He's back to his best now and is helping Liverpool fight for the title this season.