4: Carlos Tevez
Man Utd: 99 appearances, 34 goals (2007 - 2009)
Juventus: 96 appearances, 50 goals (2013 - 2015)
Carlos Tevez played a crucial role during one of the greatest seasons in United history in 2007/08 as the club won a Premier League and Champions League double. He was bizarrely only on loan, however, and when the time came to buy him outright in 2009, United declined.
The deal required United to pay £25m for the Argentine and Sir Alex Ferguson famously felt the proposed arrangement didn't offer any value, stating in an interview with The Guardian at the time: "I was happy to go along with the deal as long as it was the right one but, quite simply, he is not worth £25m."
After spending four years with United's fierce crosstown rivals, Manchester City, Tevez moved on to Juventus in 2013 and won Serie A in each of his two seasons in Italy, as well appearing in the 2015 Champions League final for the club.