| From | Team | Fee | Apps | Goals | To | |
|---|---|---|---|---|---|---|
| 2006 | AEK Athens | - | 38 | 1 | 2009 | (Player) |
| 2009 | Genoa | - | 51 | 2 | 2010 | (Player) |
| 2010 | AC Milan | £12,300,000 | 5 | 0 | 2011 | (Player) |
| 2011 | Genoa | £11,400,000 | 0 | 0 | 2012 | (Player) |
| 2011 | Werder Bremen | Loan | 30 | 1 | 2012 | (On loan) |
| 2012 | Werder Bremen | £4,400,000 | 29 | 1 | 2013 | (Player) |
| 2013 | Borussia Dortmund | £8,300,000 | 130 | 7 | 2018 | (Player) |
| 2018 | Arsenal | £17,700,000 | 44 | 3 | 2021 | (Player) |
| 2020 | Arsenal U21 | - | 0 | 0 | 2021 | (Player) |
| 2021 | Olympiakos | Free | 66 | 4 | 2023 | (Player) |
| 2023 | Real Betis | - | 15 | 0 | 2024 | (Player) |