The deal runs until January 2 and does not include a clause allowing Birmingham to recall the 29-year-old, who is in the last year of his contract at St Andrew's.
Duffy joined Birmingham from Doncaster Rovers a year ago, but made just one Championship start in his debut campaign.
He also had a brief loan spell in League One with Chesterfield in February earlier this year.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Wycombe WanderersWycombe | 15 | 11 | 2 | 2 | 35 | 18 | 17 | 35 |
| 2 | Wrexham | 16 | 9 | 4 | 3 | 25 | 11 | 14 | 31 |
| 3 | Stockport CountyStockport | 17 | 8 | 6 | 3 | 29 | 17 | 12 | 30 |
| 4 | Birmingham CityBirmingham | 14 | 9 | 3 | 2 | 26 | 15 | 11 | 30 |
| 5 | Huddersfield TownHuddersfield | 15 | 8 | 2 | 5 | 23 | 15 | 8 | 26 |
| 6 | Barnsley | 16 | 7 | 5 | 4 | 24 | 20 | 4 | 26 |
| 7 | Lincoln CityLincoln | 16 | 7 | 5 | 4 | 23 | 20 | 3 | 26 |
| 8 | Reading | 15 | 8 | 2 | 5 | 24 | 22 | 2 | 26 |
| 9 | Bolton WanderersBolton | 15 | 8 | 2 | 5 | 24 | 25 | -1 | 26 |
| 10 | Mansfield TownMansfield | 14 | 7 | 3 | 4 | 20 | 16 | 4 | 24 |
| 11 | Exeter CityExeter | 15 | 7 | 2 | 6 | 14 | 13 | 1 | 23 |
| 12 | Peterborough UnitedPeterborough | 16 | 6 | 3 | 7 | 32 | 29 | 3 | 21 |
| 13 | Bristol Rovers | 16 | 6 | 3 | 7 | 17 | 21 | -4 | 21 |
| 14 | Charlton AthleticCharlton | 15 | 5 | 4 | 6 | 16 | 17 | -1 | 19 |
| 15 | Stevenage | 16 | 5 | 4 | 7 | 11 | 16 | -5 | 19 |
| 16 | Northampton TownNorthampton | 16 | 4 | 6 | 6 | 18 | 21 | -3 | 18 |
| 17 | Wigan AthleticWigan | 15 | 4 | 5 | 6 | 13 | 12 | 1 | 17 |
| 18 | Rotherham UnitedRotherham | 16 | 4 | 5 | 7 | 14 | 19 | -5 | 17 |
| 19 | Blackpool | 16 | 4 | 5 | 7 | 22 | 30 | -8 | 17 |
| 20 | Crawley TownCrawley | 17 | 4 | 4 | 9 | 15 | 27 | -12 | 16 |
| 21 | Leyton Orient | 15 | 4 | 3 | 8 | 14 | 18 | -4 | 15 |
| 22 | Cambridge UnitedCambridge | 15 | 3 | 3 | 9 | 13 | 24 | -11 | 12 |
| 23 | Shrewsbury TownShrewsbury | 16 | 3 | 2 | 11 | 16 | 29 | -13 | 11 |
| 24 | Burton Albion | 15 | 1 | 5 | 9 | 15 | 28 | -13 | 8 |
| > League One Full Table | |||||||||
