The 24-year-old picked up the injury during his side's 3-3 draw with Newcastle United on New Year's Day.
A statement on the club's official Twitter feed has not said how serious the damage is, but the Irishman will be ruled out "indefinitely".
Long has made just two appearances in the Premier League for the Clarets this season.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Sheffield UnitedSheff Utd | 20 | 13 | 5 | 2 | 28 | 11 | 17 | 42 |
| 2 | Leeds UnitedLeeds | 20 | 12 | 5 | 3 | 36 | 14 | 22 | 41 |
| 3 | Burnley | 20 | 10 | 8 | 2 | 24 | 7 | 17 | 38 |
| 4 | Sunderland | 20 | 10 | 7 | 3 | 29 | 15 | 14 | 37 |
| 5 | Blackburn RoversBlackburn | 19 | 10 | 4 | 5 | 23 | 17 | 6 | 34 |
| 6 | West Bromwich AlbionWest Brom | 20 | 7 | 11 | 2 | 23 | 14 | 9 | 32 |
| 7 | Middlesbrough | 20 | 9 | 4 | 7 | 34 | 25 | 9 | 31 |
| 8 | Watford | 19 | 9 | 4 | 6 | 27 | 25 | 2 | 31 |
| 9 | Swansea CitySwansea | 20 | 7 | 6 | 7 | 21 | 19 | 2 | 27 |
| 10 | Norwich CityNorwich | 20 | 6 | 8 | 6 | 35 | 30 | 5 | 26 |
| 11 | Bristol City | 20 | 6 | 8 | 6 | 25 | 25 | 0 | 26 |
| 12 | Sheffield WednesdaySheff Weds | 20 | 7 | 5 | 8 | 23 | 29 | -6 | 26 |
| 13 | Millwall | 19 | 6 | 7 | 6 | 20 | 17 | 3 | 25 |
| 14 | Preston North EndPreston | 20 | 4 | 10 | 6 | 20 | 26 | -6 | 22 |
| 15 | Luton TownLuton | 20 | 6 | 4 | 10 | 23 | 35 | -12 | 22 |
| 16 | Coventry CityCoventry | 20 | 5 | 6 | 9 | 25 | 29 | -4 | 21 |
| 17 | Derby CountyDerby | 20 | 5 | 6 | 9 | 22 | 26 | -4 | 21 |
| 18 | Stoke CityStoke | 20 | 5 | 6 | 9 | 21 | 26 | -5 | 21 |
| 19 | Queens Park RangersQPR | 20 | 4 | 9 | 7 | 20 | 26 | -6 | 21 |
| 20 | Oxford UnitedOxford Utd | 19 | 4 | 6 | 9 | 20 | 30 | -10 | 18 |
| 21 | Portsmouth | 18 | 3 | 8 | 7 | 21 | 30 | -9 | 17 |
| 22 | Cardiff CityCardiff | 19 | 4 | 5 | 10 | 17 | 30 | -13 | 17 |
| 23 | Plymouth ArgylePlymouth | 19 | 4 | 5 | 10 | 19 | 40 | -21 | 17 |
| 24 | Hull City | 20 | 3 | 7 | 10 | 18 | 28 | -10 | 16 |
| > Championship Full Table | |||||||||
