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 | Sheffield UnitedSheff Utd | 17 | 11 | 4 | 2 | 24 | 9 | 15 | 35 |
| 2 | Burnley | 17 | 9 | 6 | 2 | 21 | 6 | 15 | 33 |
| 3 | Sunderland | 17 | 9 | 6 | 2 | 26 | 12 | 14 | 33 |
| 4 | Leeds UnitedLeeds | 16 | 9 | 5 | 2 | 28 | 12 | 16 | 32 |
| 5 | Watford | 17 | 9 | 2 | 6 | 26 | 24 | 2 | 29 |
| 6 | Middlesbrough | 16 | 8 | 3 | 5 | 29 | 19 | 10 | 27 |
| 7 | West Bromwich AlbionWest Brom | 17 | 6 | 9 | 2 | 18 | 11 | 7 | 27 |
| 8 | Millwall | 16 | 6 | 6 | 4 | 19 | 14 | 5 | 24 |
| 9 | Norwich CityNorwich | 17 | 5 | 7 | 5 | 31 | 25 | 6 | 22 |
| 10 | Blackburn RoversBlackburn | 15 | 6 | 4 | 5 | 19 | 17 | 2 | 22 |
| 11 | Bristol City | 17 | 5 | 7 | 5 | 20 | 21 | -1 | 22 |
| 12 | Sheffield WednesdaySheff Weds | 17 | 6 | 4 | 7 | 20 | 26 | -6 | 22 |
| 13 | Stoke CityStoke | 17 | 5 | 6 | 6 | 19 | 20 | -1 | 21 |
| 14 | Derby CountyDerby | 16 | 5 | 5 | 6 | 20 | 20 | 0 | 20 |
| 15 | Swansea CitySwansea | 16 | 5 | 4 | 7 | 14 | 14 | 0 | 19 |
| 16 | Luton TownLuton | 16 | 5 | 3 | 8 | 18 | 26 | -8 | 18 |
| 17 | Coventry CityCoventry | 17 | 4 | 5 | 8 | 22 | 25 | -3 | 17 |
| 18 | Oxford UnitedOxford Utd | 17 | 4 | 5 | 8 | 19 | 27 | -8 | 17 |
| 19 | Preston North EndPreston | 17 | 3 | 8 | 6 | 16 | 24 | -8 | 17 |
| 20 | Plymouth ArgylePlymouth | 17 | 4 | 5 | 8 | 18 | 34 | -16 | 17 |
| 21 | Cardiff CityCardiff | 16 | 4 | 4 | 8 | 15 | 24 | -9 | 16 |
| 22 | Hull City | 17 | 3 | 6 | 8 | 16 | 23 | -7 | 15 |
| 23 | Portsmouth | 15 | 2 | 6 | 7 | 16 | 28 | -12 | 12 |
| 24 | Queens Park RangersQPR | 16 | 1 | 8 | 7 | 13 | 26 | -13 | 11 |
| > Championship Full Table | |||||||||
