Never go back? Here's 10 players who did
David Luiz has returned to Chelsea from Paris St Germain, a little more than two years after joining the French champions for £50million - a world-record fee for a defender.
Here, Press Association Sport looks at 10 other high-profile players who have returned to a former club - including one who has been part of a previous deal involving Luiz and the Blues.
Initially cost Chelsea £1.5million from MFK Kosice and was then swapped for Luiz - then at Benfica - two years later. The Blues saw the error of their ways in 2014 when they shelled out £21million to bring the Serbia midfielder back to Stamford Bridge.
Henry played for the Gunners from 1999 until 2007. The club's record goalscorer, he saw a statue of himself unveiled outside the Emirates only weeks before returning on loan for six weeks from New York Red Bulls in January 2012. The striker was only on the pitch for 10 minutes in his 'second debut', the FA Cup replay against Leeds, before he scored - and finished the stint in style, scoring a last-minute goal to give Arsenal a win at Sunderland.
After scoring 207 goals for Liverpool between 1980 and 1987, the Welshman left for Juventus for a British record transfer fee of £3.2m. Rush never fully settled in Italy - scoring only 14 goals - and was sold back to Liverpool in 1988 for £2.7million. He added another 139 goals to his Anfield tally before leaving in 1996.
Ferguson was initially bought by Everton in 1994, just after he had finished a three-month prison sentence for headbutting a player in Scotland. He soon endeared himself to the Everton faithful in his original four-year stint at the club, but left for Newcastle. After a lacklustre 18 months on Tyneside, he was soon back at Everton, where he stayed until his retirement in 2006. H is now an assistant coach at the Merseyside club.
After spending his youth as a Barcelona player, the much-heralded, long-awaited homecoming of Fabregas to the Catalan club in 2011 did not pan out the way many hoped. The young midfielder, in a deal worth a potential £35million to Arsenal, was seen as a ready-made replacement for Barcelona's midfield stars but never found the same level of quality he had produced with the Gunners and was sold to Chelsea three years later.
GRAEME LE SAUX
Sold by Chelsea to Blackburn for just £700,000 after throwing his shirt at manager Ian Porterfield in protest at being substituted, Le Saux became the most expensive defender in England when the Blues forked out £5million to bring him back.
Newcastle had a young Shearer growing up on their doorstep and offered him a trial. However, the story goes that they put him in goal. Southampton had the foresight to play Shearer up front and promptly signed the future England captain. When Newcastle finally got their man - from Blackburn, in 1996 - it cost them a then world-record £15million.
Cole was the product of the West Ham youth system and Manchester United reportedly offered them £10million for his services as a 16-year-old. The former England midfielder, whose playing style had been likened to that of Paul Gascoigne, left the Hammers in a £6.6million deal in 2003 for Chelsea, where he spent seven years. He rejoined West Ham on a free transfer from Liverpool three years later but was released at the end of his 18-month contract.
Defoe's return Tottenham looked unlikely after a move to Portsmouth in January 2008, when the club opted to buy Darren Bent for more than £16million. After deciding Bent was not the answer to their striking problems, Spurs soon came back in for Defoe, buying him back for £8million more than they had sold him for 18 months earlier.
Earlier this month Paul Pogba once again became a Manchester United player, signing from Juventus in a world-record deal worth 105million euros (£89million) four years after leaving Old Trafford for just £800,000.