When it comes to selling players, most clubs usually do it to try and get rid of players when they are on a downward spiral.
Arsene Wenger sold the likes of Thierry Henry and Patrick Vieira just as they were past their best. While Sir Alex Ferguson replaced worn out legs with new signings after a successful campaign.
There is something of an art to it, but it is an art that Chelsea, despite their success, have never quite been able to master.
1. Romelu Lukaku
A £10million signing from Belgium, Lukaku played just 15 games for Chelsea before they discarded him in 2012.
With Loan spells at West Brom and Everton, the Londoners never deemed it fit to keep him. But after completing his permanent move to Everton, he became a Premier League star with 54 goals in 106 appearances during his 3 years on Merseyside.
With Lukaku now at Manchester United, a player Chelsea had struggled all summer to re-sign, they seem set to regret letting another one get away.
2. Kevin De Bruyne
Signed in 2012 from Genk, the midfielder was immediately tipped for big things at Stamford Bridge. However things didn’t turn out to be so as he was never given a consistent chance to prove himself other than a brief spell under Jose Mourinho at the beginning of the 2012/13 season.
The Belgian was first sent on loan to Bremen in 2013 before being sold off to Wolfsburg in winter of 2014. De Bruyne scored 10 goals with over 20 assists in his first full season with Wolfsburg.
Since his reappearance in the Premier League 18 months later at Manchester City, he’s turned into one of the best attacking midfielders in the division.
3. Mohammed Salah
Liverpool have brought back Egyptian winger Mohammed Salah to the Premier League for a club record fee. It provides further proof that Chelsea might just have been a bit too quick to judge the player after letting him go only just a year after signing him from Basel in 2014.
But having scored 15 goals and made 11 assists for Roma in Serie A last season, he looks set to add further bite to Liverpool’s attack in the new campaign as they aim to win the English Premier League.