3. Mats Hummels: Bayern Munich to Borussia Dortmund – The World Cup winner came through Bayerns youth academy, playing just one Bundesliga game before joining Borussia Dortmund initially on loan. The defender went from strength to strength, leading Jurgen Klopps side to back-to-back titles from 2010-2012 and he was a pivotal part of the Germany squad that lifted the World Cup in Brazil last year. 6 6 6. Eric Cantona: Leeds United to Manchester United Click the arrow to see more players clubs are likely to have regretted selling – Leeds inexplicably allowed the Frenchman to leave Elland Road for Man United in November 1992. Leeds chairman Bill Fotherby phoned United to enquire about the availability of Denis Irwin, but ended up selling their star performer. Despite some questionable off-the-pitch antics, Cantona enjoyed great success at Old Trafford winning four league titles and two FA cups. 2. Daniel Sturridge: Chelsea to Liverpool – The Englishman was inexplicably allowed to leave twice, first from Man City to Chelsea on a free transfer. But after struggling to hold down a first-team place often played out-wide Sturridge moved to Liverpool in 2013 for just £12m. And the 25-year-old has been in sensational form ever since, bagging 37 goals in just 55 matches in all competitions including a career-high 24 goals last season as the Reds came agonisingly close to winning the Premier League. 4. Arjen Robben: Real Madrid to Bayern Munich – The Netherlands international never quite found his top form at the Santiago Bernebeu scoring just 11 league goals in 50 appearances. Robben joined the German champions in 2009 for around 25m and has gone on to establish himself as one of the worlds elite wingers, scoring 68 times in 122 games and winning 11 major honours. 5. Frank Lampard: Chelsea to New York City FC (via Manchester City) – Chelseas decision to release their all-time leading goalscorer last summer after 13 years took many by surprise, especially with the Englishman revealing he was to move to the MLS with New York City FC. However, Lampard eventually joined NYC parent club and Chelseas domestic rivals, Manchester City, for the season and the midfielder has become a valuable player for the Citizens, even scoring against the Blues at the Etihad earlier this season. 6 Wolfsburg general manager Klaus Allofs believes Chelsea regret letting Kevin De Bruyne leave, after the Belgian’s brilliant form this season.The 23-year-old Belgium international made just three Premier League appearances at Stamford Bridge before being sold to the Bundesliga side in January 2014.A fee of £18m represented good business for the Blues, but with eight league goals and 12 assists already this season, will the decision to let a talented young player who is thriving this season, come back to haunt them.Notable mentions:Gary Cahill: Aston Villa to Bolton to Chelsea – Cahill was never able to establish himself as a regular at Aston Villa and was eventually sold to Bolton in 2007. He moved to Chelsea in 2011, where the central defender has won medals and become a regular for the England national side. How Villa could use him now!Gerard Pique: Manchester United to Barcelona – The Spaniard made just 12 league appearances at Old Trafford before moving back to Barcelona in 2008. He has since gone to lead club and country to unrivalled success.Nemanja Matic: Chelsea to Benfica – Although back at Chelsea now, the Blues let the Serbian leave in 2009 as part of the deal that brought David Luiz to Stamford Bridge. Jose Mourinho eventually saw the midfielder’s worth and re-signed Matic for £21million last season, and he has established himself as one of the best defensive midfielders in the Premier League.Click the arrow to see a list of six current and former players that clubs are likely to have regretted selling or allowing to leave on free transfers and let us know which player you regret your club getting rid of? 6 6 6 1. Paul Pogba: Manchester United to Juventus – The France international managed just three Premier League appearances for United before joining Juventus on a free transfer in July 2012. Sir Alex Ferguson was reportedly unhappy with Pogbas wage demands at the time, but the Scots decision may be one of the worst of his Old Trafford tenure, as Pogba has since established himself as one of the best midfielders in the world. The Frenchman is energetic and powerful and exactly what Uniteds midfield is missing and a world record fee is being mooted to tempt Pogba away from Turin.