The 25-year-old Jamaican, who is a product of the Hornets' youth academy, impressed Royals boss Brian McDermott with a string of solid performances last season.
The newly-promoted Berkshire club have offered Watford £2m for the player and that has been rejected, according to Sky Sports News.
Mariappa has made 247 appearances for Watford in seven seasons at Vicarage Road.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | West Bromwich AlbionWest Brom | 5 | 4 | 1 | 0 | 9 | 2 | 7 | 13 |
| 2 | Sunderland | 5 | 4 | 0 | 1 | 12 | 4 | 8 | 12 |
| 3 | Blackburn RoversBlackburn | 5 | 3 | 2 | 0 | 12 | 6 | 6 | 11 |
| 4 | Burnley | 5 | 3 | 1 | 1 | 11 | 3 | 8 | 10 |
| 5 | Watford | 5 | 3 | 1 | 1 | 9 | 5 | 4 | 10 |
| 6 | Sheffield UnitedSheff Utd | 5 | 3 | 2 | 0 | 8 | 3 | 5 | 9 |
| 7 | Oxford UnitedOxford Utd | 5 | 3 | 0 | 2 | 9 | 6 | 3 | 9 |
| 8 | Derby CountyDerby | 5 | 3 | 0 | 2 | 8 | 6 | 2 | 9 |
| 9 | Leeds UnitedLeeds | 5 | 2 | 2 | 1 | 7 | 4 | 3 | 8 |
| 10 | Middlesbrough | 5 | 2 | 2 | 1 | 6 | 4 | 2 | 8 |
| 11 | Swansea CitySwansea | 5 | 2 | 1 | 2 | 5 | 3 | 2 | 7 |
| 12 | Queens Park RangersQPR | 5 | 1 | 3 | 1 | 7 | 8 | -1 | 6 |
| 13 | Hull City | 6 | 1 | 3 | 2 | 5 | 7 | -2 | 6 |
| 14 | Stoke CityStoke | 6 | 2 | 0 | 4 | 4 | 9 | -5 | 6 |
| 15 | Coventry CityCoventry | 5 | 1 | 2 | 2 | 5 | 6 | -1 | 5 |
| 16 | Norwich CityNorwich | 5 | 1 | 2 | 2 | 4 | 6 | -2 | 5 |
| 17 | Plymouth ArgylePlymouth | 5 | 1 | 2 | 2 | 5 | 9 | -4 | 5 |
| 18 | Bristol City | 5 | 1 | 2 | 2 | 6 | 11 | -5 | 5 |
| 19 | Millwall | 5 | 1 | 1 | 3 | 8 | 8 | 0 | 4 |
| 20 | Luton TownLuton | 5 | 1 | 1 | 3 | 3 | 7 | -4 | 4 |
| 21 | Sheffield WednesdaySheff Weds | 5 | 1 | 1 | 3 | 5 | 10 | -5 | 4 |
| 22 | Preston North EndPreston | 5 | 1 | 1 | 3 | 3 | 9 | -6 | 4 |
| 23 | Portsmouth | 5 | 0 | 3 | 2 | 6 | 11 | -5 | 3 |
| 24 | Cardiff CityCardiff | 5 | 0 | 1 | 4 | 1 | 11 | -10 | 1 |
| > Championship Full Table | |||||||||
