Didn't Bayern Munich supposedly have one in the contract for Emre Can?
Here's something from "The Knowledge" column in The Guardian:
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http://www.theguardian.com/football...ge-football-clubs-activating-buy-back-clauses
Which football clubs have activated transfer buy-back clauses?
Simon Burnton
theguardian.com, Wednesday 4 December 2013 00.08 GMT
"Ravel Morrison has impressed for West Ham United this season and some Manchester United fans are disappointed that he does not have a buy-back clause in his contract but has any club actually triggered a buy-back clause and brought a player back?" wonders Sean Kirrane.
British clubs have been sticking buy-back clauses into transfer deals for some time, even if they weren't always sure they could get away with it. "I would not like to say whether this agreement is legally binding. It could possibly be considered a restraint of trade," said the Liverpool secretary, Peter Robinson, after he slipped one into the deal that took Kevin Keegan to Hamburg in 1977. "But it was willingly signed by Kevin, who has said that he would not do anything without talking to us." When the future England manager decided to return to England in 1980 – snubbing other options on the continent to be sure of his England place and because his wife was worried that he might be kidnapped if they moved to Italy – he had to phone the Liverpool chairman, John Smith, to get his permission to join Southampton.
The first example of an exploited buy-back clause in British football, or at least the earliest we've managed to truffle out, involved the England striker Luther Blissett, sold by Watford to Milan in the summer of 1983 having just top-scored in ye olde First Division with 27 goals. The following March, the player having mustered three goals in 22 appearances so undistinguished that rumours circled suggesting that the Italian side had bought him by accident when they really wanted John Barnes, he was put on the transfer list. Towards the end of his time in Italy the Milan president, Giuseppe Farina, was asked what his opinion was on the quality of English players. "They are only good for the Falklands," he sneered.
"At Watford you'd get four or five shots every game and you might score from one," Blissett complained of life in Serie A. "In some games here you're lucky if you get a single chance and it's usually no more than a half-chance. I keep telling them to knock the ball over the top but they won't risk it. They're scared to hit 30-yard balls in case they lose possession. It couldn't be more different from Watford."
"Watford, who have a buy-back clause in Blissett's contract, would undoubtedly be his first choice," reported the Times at the time. "'Of course I would like to go back there,' he said. 'I have very happy memories of Watford and I still have a great feeling for the club. But Milan would obviously want to recoup some of the transfer fee they paid for me and whether Watford could afford me is another matter.'" They could and the £550,000 it took to return him to Hertfordshire represented a smart £450,000 profit.
Ian Rush followed Blissett in making a short-term move to Italy before returning to the club that sold him but Liverpool's first option was only informally agreed whereas, though Tottenham wrote a buy-back clause into the deal that took Glenn Hoddle to Monaco in 1987, by the time he left France he was 33 and next played for Swindon. So the next high-profile British-club-involving completed buy-back involved Trevor Steven, the England full-back sold by Rangers to Marseille for £5m in the summer of 1991. Eleven months later he was back, a victim of the financial turmoil engulfing the French club at the time. They had paid only £2.8m of his fee and Rangers secured his return simply by writing off the missing £2.2m. "We insisted on having the first option on Trevor in our agreement with Marseille," said David Murray, the Rangers chairman, in December 1991. "The final payment from them is due on 31 March but we all know that French football is in a bad way. If they can't make the payment, we'd be delighted to have him back."
The buy-back continued to be most popular in international transfers, with Middlesbrough inserting one into the small print of the £12m deal they struck with Atlético Madrid to sell Juninho in 1997. "We have first option to buy back Juninho during the period of his contract," their chief executive, Keith Lamb, confirmed. "That option is not there for show. It's there because we have a genuine interest. If he wants to leave Spain, we can have him back here at Middlesbrough."
His time in Madrid was not enormously successful – he broke his leg and Claudio Ranieri didn't think much of him – and by the end of 1998 talks over a potential return were an open secret. Even though he said he didn't particularly want to go back, Bryan Robson insisted a £10.5m deal was "a couple of weeks" away in early 1999. He was a little over-confident, as was the player's agent when a move to Aston Villa was in the offing that summer – the agent insisted he was "90% certain the deal would go through", to which the Villa manager, John Gregory, responded: "He's getting a bit carried away. I'd say it's about 50-50." It turned out to be more like 0-100. Finally in August he did return to the Riverside, on loan with a view to a permanent deal, but his fitness was questionable, his impact limited and that permanent deal didn't immediately transpire. Instead there followed a couple of loans back to Brazil before, in 2002, that old clause was indeed triggered and he rejoined for £3.8m.
So much for relatively distant buy-backs. The most recent high-profile example, as Christopher Davies and many others pointed out, is Daniel Carvajal. "He was sold to Bayern Leverkusen for €5m in the summer of 2012 and played there for exactly one season, becoming the third best right-back in the Bundesliga according to a fans' poll behind Phillip Lahm of Bayern Munich and Atsuto Uchide of Schalke," Christopher writes. "He became Real Madrid's first signing this summer for around €6.5m." Carvajal has since worked his way into Real's first team and has played every minute of their last three league matches. Other examples in Spain, where the buy-back seems as common as cold soup, include Luis García's return from Atlético Madrid to Barcelona in 2003 and Esteban Granero's swift switchback from Getafe in 2009.
