Considered as one of the best midfielders of his generation, Ballack joined Chelsea from Bayern Munich on a free transfer in the summer of 2006 during Jose Mourinho’s first spell as Chelsea boss.
Ballack spent four seasons at Stamford Bridge, winning the Premier League, two FA Cups, League Cup and finishing on the losing side in the 2008 UEFA Champions League final when Manchester United defeated the Blues on penalties in Moscow.
Ballack’s time at Chelsea concluded at the end of the 2009/2010 season, when he got injured in the FA Cup final victory over Portsmouth following a tackle from Kevin-Prince Boateng and subsequently missed that summer’s FIFA World Cup in South Africa.
While Chelsea were willing to extend Ballack’s stay by a year, the-then 33-year-old wanted a two-year extension to his expiring contract and an agreement could not be reached between the two parties.
Ballack returned to Germany, signing for Bayer Leverkusen before calling time on his career two years later.
Now 43, Ballack has admitted he was wrong to leave West London and would have liked to retire at Chelsea.
Ballack, speaking on Sky Sports' Transfer Talk podcast, said: 'Carlo wanted me [to stay] but the club made a decision to only give players of that age a one-year contract. I wanted two.
'Today, I can say maybe it was wrong. I should have stayed, even for that one year.
'I could never imagine that I would go back to [Bayer] Leverkusen. Until the last day, I actually thought we would find a way at Chelsea. I was really hoping I could stay until the end.'
