The 29-year-old defender joined the Red Devils back in September on an emergency deal.
Sadler has made seven appearances in all competitions for John Gregory's side during his time at Broadfield Stadium.
Crawley continue their League One campaign on Saturday when they make the trip to Notts County.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Birmingham CityBirmingham | 37 | 26 | 8 | 3 | 63 | 25 | 38 | 86 |
| 2 | Wrexham | 39 | 23 | 8 | 8 | 54 | 30 | 24 | 77 |
| 3 | Wycombe WanderersWycombe | 38 | 21 | 11 | 6 | 65 | 36 | 29 | 74 |
| 4 | Charlton AthleticCharlton | 39 | 20 | 9 | 10 | 53 | 35 | 18 | 69 |
| 5 | Stockport CountyStockport | 39 | 19 | 11 | 9 | 55 | 36 | 19 | 68 |
| 6 | Reading | 38 | 17 | 11 | 10 | 55 | 47 | 8 | 62 |
| 7 | Huddersfield TownHuddersfield | 38 | 18 | 7 | 13 | 52 | 38 | 14 | 61 |
| 8 | Bolton WanderersBolton | 38 | 18 | 6 | 14 | 60 | 57 | 3 | 60 |
| 9 | Leyton Orient | 38 | 18 | 5 | 15 | 54 | 38 | 16 | 59 |
| 10 | Blackpool | 39 | 14 | 15 | 10 | 59 | 51 | 8 | 57 |
| 11 | Barnsley | 39 | 15 | 9 | 15 | 53 | 55 | -2 | 54 |
| 12 | Lincoln CityLincoln | 39 | 13 | 11 | 15 | 53 | 46 | 7 | 50 |
| 13 | Stevenage | 38 | 13 | 10 | 15 | 35 | 39 | -4 | 49 |
| 14 | Mansfield TownMansfield | 38 | 13 | 8 | 17 | 45 | 52 | -7 | 47 |
| 15 | Peterborough UnitedPeterborough | 38 | 12 | 9 | 17 | 57 | 63 | -6 | 45 |
| 16 | Rotherham UnitedRotherham | 38 | 12 | 9 | 17 | 42 | 49 | -7 | 45 |
| 17 | Exeter CityExeter | 38 | 12 | 9 | 17 | 40 | 53 | -13 | 45 |
| 18 | Wigan AthleticWigan | 37 | 11 | 11 | 15 | 34 | 37 | -3 | 44 |
| 19 | Northampton TownNorthampton | 39 | 10 | 13 | 16 | 38 | 57 | -19 | 43 |
| 20 | Bristol Rovers | 39 | 12 | 6 | 21 | 40 | 63 | -23 | 42 |
| 21 | Burton Albion | 38 | 8 | 12 | 18 | 39 | 55 | -16 | 36 |
| 22 | Crawley TownCrawley | 39 | 9 | 9 | 21 | 44 | 71 | -27 | 36 |
| 23 | Cambridge UnitedCambridge | 39 | 7 | 10 | 22 | 37 | 63 | -26 | 31 |
| 24 | Shrewsbury TownShrewsbury | 38 | 7 | 7 | 24 | 35 | 66 | -31 | 28 |
| > League One Full Table | |||||||||
