The Mexico international spent last season on loan with the Portuguese club, for whom he made 27 league appearances.
Layun's performances were good enough to convince the Porto hierarchy to turn the switch into a permanent one for a fee believed to be around £4m.
It is thought that Watford have negotiated a 20% sell-on clause as part of the deal.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Sunderland | 8 | 6 | 0 | 2 | 16 | 6 | 10 | 18 |
| 2 | Burnley | 8 | 5 | 2 | 1 | 14 | 4 | 10 | 17 |
| 3 | Sheffield UnitedSheff Utd | 8 | 5 | 3 | 0 | 10 | 3 | 7 | 16 |
| 4 | West Bromwich AlbionWest Brom | 8 | 5 | 1 | 2 | 12 | 6 | 6 | 16 |
| 5 | Leeds UnitedLeeds | 8 | 4 | 3 | 1 | 13 | 5 | 8 | 15 |
| 6 | Blackburn RoversBlackburn | 8 | 4 | 3 | 1 | 14 | 9 | 5 | 15 |
| 7 | Middlesbrough | 8 | 4 | 2 | 2 | 9 | 5 | 4 | 14 |
| 8 | Watford | 8 | 4 | 1 | 3 | 12 | 13 | -1 | 13 |
| 9 | Hull City | 8 | 3 | 3 | 2 | 12 | 9 | 3 | 12 |
| 10 | Norwich CityNorwich | 8 | 3 | 3 | 2 | 12 | 10 | 2 | 12 |
| 11 | Oxford UnitedOxford Utd | 8 | 3 | 2 | 3 | 12 | 10 | 2 | 11 |
| 12 | Swansea CitySwansea | 8 | 3 | 2 | 3 | 8 | 6 | 2 | 11 |
| 13 | Bristol City | 8 | 2 | 4 | 2 | 9 | 13 | -4 | 10 |
| 14 | Stoke CityStoke | 8 | 3 | 0 | 5 | 10 | 12 | -2 | 9 |
| 15 | Derby CountyDerby | 8 | 3 | 0 | 5 | 10 | 12 | -2 | 9 |
| 16 | Millwall | 8 | 2 | 2 | 4 | 12 | 11 | 1 | 8 |
| 17 | Coventry CityCoventry | 8 | 2 | 2 | 4 | 9 | 11 | -2 | 8 |
| 18 | Plymouth ArgylePlymouth | 8 | 2 | 2 | 4 | 8 | 12 | -4 | 8 |
| 19 | Sheffield WednesdaySheff Weds | 8 | 2 | 2 | 4 | 9 | 14 | -5 | 8 |
| 20 | Luton TownLuton | 8 | 2 | 2 | 4 | 8 | 13 | -5 | 8 |
| 21 | Preston North EndPreston | 8 | 2 | 2 | 4 | 7 | 12 | -5 | 8 |
| 22 | Queens Park RangersQPR | 8 | 1 | 4 | 3 | 9 | 14 | -5 | 7 |
| 23 | Portsmouth | 8 | 0 | 4 | 4 | 8 | 19 | -11 | 4 |
| 24 | Cardiff CityCardiff | 8 | 1 | 1 | 6 | 3 | 17 | -14 | 4 |
| > Championship Full Table | |||||||||
