With each of the Premier League sides eligible to select a 25-man squad for the season, as of the rule change in 2010, any player under the age of 21 does not count towards this.
Watford, who have been somewhat infamous for their transfer policies in the past, have a number of superbly talented youngster on their books, who won’t count towards their 25-man squad, and are worth watching out for this campaign.
Javi Gracia’s side were riddled with injuries last season, with a report by Sky Sports stating they lost a combined 1,871 days through knocks - the most in England’s top flight - making this loophole ever more appealing for the Hornets.
With that in mind, here is a look at seven youngsters, all under the age of 21, to keep an eye out for in the Watford squad this season.
7. Pontus Dahlberg
Pontus Dahlberg signed for Watford in January 2018 on a five-and-a-half year contract, and is certainly one to keep an eye on.
The 19-year-old Swedish shot stopper has been training with the Hornets first team squad during preseason, and while many believe that new signing Ben Foster will be the new first choice, the young Swede might just take the number one jersey.
The young keeper already has a full international appearance for his country, and spent previous season on loan at his former side IFK Goteborg.
6. Ben Wilmot
Ben Wilmot, formerly of fellow Herefordshire side Stevenage, signed for Watford in May this year on a five-year deal - reportedly worth around £1m - despite interest from a number of other Premier League clubs including Tottenham Hotspur.
The 18-year-old centre back began his career through the Stevenage academy, making his debut for his boyhood club in October 2017.
Wilmot received an unexpected, but fully deserved, call up to represent England Under-19’s in March for their 2018 European Championship qualification, making his debut in a 3-0 victory against Latvia.
5. Pervis Estupinan
Pervis Estupinan, who has never having made an appearance for Watford since signing at Vicarage Road back in July 2016, spent this season on loan at Segunda Division side UD Almeria where he made 26 appearances.
The 20-year-old left back, who has been subject to bids from Porto and Sporting CP, made two La Liga appearances in during his loan spell at Watford’s former sister club Granada, with his debut coming against Deportivo de la Coruna in April 2017.
Estupinan also has seven goals in his 22 appearances across multiple youth levels for Ecuador – not a bad record for a defender!
4. Lewis Gordon
The 17-year-old might not be a starter for Javi Gracia’s side this coming season, but after signing his first professional contract at Vicarage Road in March, he might feature periodically throughout the campaign.
Gordon, who has been at club since the age of seven, progressed through the ranks last season, making appearances for the Under-18’s and the Under-23’s, even scoring the winning goal for the former in their FA Youth Cup tie with Sunderland.
The young versatile player, who received a call up to the Scotland Under-17’s side as a result of his impressive individual campaign, was part of the first team squad for their preseason friendly against Wimbledon, coming on as a second half substitute.
3. Dodi Lukebakio
The 20-year-old winger signed for Watford in January 2018 on a four-and-a-half year contract, and while he only managed one appearance in the second half of the Premier League season for his new club, is certainly one to keep an eye out for.
Lukebakio, who made his name playing for Belgian First Division side Anderlecht, is an exciting young prospect for the Hornets with blistering pace and bags of potential.
The young wide man has made seven appearances for the Belgium Under-21 squad since making his debut last year, and has found the net twice thus far.
2. Adalberto Peñaranda
Adalberto Peñaranda signed for the Hornets back in 2016, but due to ongoing issues with work permit, is yet to make an appearance for the club, despite such huge expectations for the player.
The 21-year-old Venezuelan is training with Watford during their preseason camp, giving Hornets fans hope this could be the year he finally breaks into the first team.
The young forward enjoyed loan spells at Granada and Udinese, before signing for his current side Malaga on loan, but the Watford faithful hope he can provide competition for places anywhere across the front three.
Brazilian wonderkid Richarlison set the Premier League alight in the opening few months of last season, with the likes of Manchester United, Bayern Munich and Juventus being linked with impending interest.
Despite his form falling away in the latter stages of the season, the potential of the 21-year-old forward is second to none, and with four years still left on his contract, won’t come cheap for any possible buyers.
Richarlison started 32 matches for the Hornets in the Premier League last campaign, finding the net five times and contributing four assists.