The Spanish Under-19 international will remain with the Championship side until January to gain first-team experience.
The 18-year-old signed his first professional contract with the Gunners last summer, and made his debut in the Capital One Cup earlier this season.
Watford sit seventh in the Championship table.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Liverpool | 6 | 5 | 0 | 1 | 12 | 2 | 10 | 15 |
| 2 | Manchester CityMan City | 6 | 4 | 2 | 0 | 14 | 6 | 8 | 14 |
| 3 | Arsenal | 6 | 4 | 2 | 0 | 12 | 5 | 7 | 14 |
| 4 | Chelsea | 6 | 4 | 1 | 1 | 15 | 7 | 8 | 13 |
| 5 | Aston Villa | 5 | 4 | 0 | 1 | 10 | 7 | 3 | 12 |
| 6 | Fulham | 6 | 3 | 2 | 1 | 8 | 5 | 3 | 11 |
| 7 | Newcastle UnitedNewcastle | 6 | 3 | 2 | 1 | 8 | 7 | 1 | 11 |
| 8 | Brighton & Hove AlbionBrighton | 6 | 2 | 3 | 1 | 10 | 8 | 2 | 9 |
| 9 | Nottingham ForestNott'm Forest | 6 | 2 | 3 | 1 | 6 | 5 | 1 | 9 |
| 10 | Tottenham HotspurSpurs | 5 | 2 | 1 | 2 | 9 | 5 | 4 | 7 |
| 11 | Manchester UnitedMan Utd | 5 | 2 | 1 | 2 | 5 | 5 | 0 | 7 |
| 12 | Brentford | 6 | 2 | 1 | 3 | 8 | 10 | -2 | 7 |
| 13 | Bournemouth | 5 | 1 | 2 | 2 | 5 | 8 | -3 | 5 |
| 14 | West Ham UnitedWest Ham | 6 | 1 | 2 | 3 | 6 | 10 | -4 | 5 |
| 15 | Everton | 6 | 1 | 1 | 4 | 7 | 15 | -8 | 4 |
| 16 | Leicester CityLeicester | 6 | 0 | 3 | 3 | 8 | 12 | -4 | 3 |
| 17 | Crystal Palace | 6 | 0 | 3 | 3 | 5 | 9 | -4 | 3 |
| 18 | Ipswich TownIpswich | 5 | 0 | 3 | 2 | 3 | 8 | -5 | 3 |
| 19 | Southampton | 5 | 0 | 1 | 4 | 2 | 9 | -7 | 1 |
| 20 | Wolverhampton WanderersWolves | 6 | 0 | 1 | 5 | 6 | 16 | -10 | 1 |
| > Premier League Full Table | |||||||||
