The players Chelsea could have made more money on
Liverpool have signed former Chelsea winger Mohamed Salah for a fee understood to be close to £35million.
The Egypt international, who has spent the last two seasons playing for Roma, left Stamford Bridge on a permanent deal last summer for less than half that figure.
Here, Press Association Sport looks at other players Chelsea could have received more money for.
1. Glen Johnson
A decade ago, England international Johnson was on his way to the south coast, leaving Chelsea to join Harry Redknapp's Portsmouth for around £4million. The fee was a couple of million less than the Blues paid West Ham for the defender in 2003 and considerably less than the amount Pompey secured when selling him on in the summer of 2009. Chelsea were interested in re-signing the right-back and had an offer accepted, but Johnson opted to sign a four-year contract with Rafa Benitez's Liverpool for around £17million.
2. Lassana Diarra
Diarra is another former Chelsea player who Portsmouth made a sizeable profit on. The France midfielder departed the Blues for an undisclosed fee - reported to be as low as £2million - in August 2007 and arrived at Fratton Park five months later via a short stay at Arsenal. Pompey, who paid the Gunners around £5.5million, almost quadrupled their money a year later, selling Diarra to LaLiga giants Real Madrid for close to £19million. Diarra lasted three seasons in the Spanish capital - his longest spell with any club - before moving on to play in Russia, France and the UAE.
3. Nemanja Matic
Chelsea admitted making a mistake with Matic. After letting him go to Benfica as a makeweight in the deal to sign Brazil defender David Luiz on the final day of January in 2011, they had to shell out around £21million to bring him back three years later. The Serbian midfielder made just two substitute appearances in the Premier League during the first spell. He has featured more than 150 times in all competitions since returning, winning two league titles and the League Cup.
4. Fabio Borini
Although the Italy international has done little in his subsequent career to suggest he would have been a playing asset for the Blues, the club missed an opportunity to capitalise financially on his departure. With his contract running down, Chelsea reportedly received less than £500,000 compensation when Borini agreed a move to Italian side Parma in 2011. His value rose considerably in the next 12 months while playing on loan at Roma and he returned to the Premier League to join Liverpool for in excess of £10million in 2012 before moving on to current club Sunderland for a slightly smaller fee.
5. Patrick van Aanholt
The left-back is currently at Crystal Palace after former Eagles boss Sam Allardyce was prompted to pay around £14million for his services in January. Van Aanholt's multi-million pound move from Sunderland to Selhurst Park came two and a half years after Chelsea let him go for around a tenth of that figure. The Holland international made only two league appearances - both as a substitute - at Stamford Bridge. He was loaned out numerous times, playing for Coventry, Newcastle, Leicester and Wigan, as well as spending two seasons with Dutch club Vitesse, before his £1.5million switch to the Stadium of Light.
6. Kevin De Bruyne
The creative midfielder became the fifth most expensive player in history when Manchester City paid Bundesliga club Wolfsburg around £55million in August 2015. Just over 18 months earlier, De Bruyne had been allowed to join the German side for less than a third of that figure by former Chelsea manager Jose Mourinho. At the time, many thought the Blues had done remarkably well to receive a reported £18million for someone who had made only three Premier League appearances, but the Belgian has since developed into one of European football's top talents.
7. Mohamed Salah
Signed for around £11million from Swiss club Basle in the 2014 January transfer window, Salah was a bit-part player for Mourinho's Chelsea. He managed two goals in 11 outings in his first season and then, after appearing only eight times the next campaign, was loaned to Fiorentina. He impressed in Florence and spent 2015/16 with Serie A rivals Roma, prior to a permanent move to the Italian capital last summer with Chelsea receiving a reported £15million. The 25-year-old will play at Anfield next season after Liverpool boss Jurgen Klopp was persuaded to part with a large chunk of his transfer budget to bring him back to England.