It is the sort of milestone that Mariappa seems almost bashful about but he admits that what has kept the club going during the tough times has been the hope of unearthing another Ashley Young or John Barnes.
"All the lads in the team were calling me the senior pro at the start of last season when I was only 22 — now I feel really old," said the Harrow-born defender. "As a club Watford have never been blessed with the funds to go out and choose any player we want, we have always had to rely on youth.
"It has been very productive with players stepping up to the first team. If a parent is choosing which academy their child should join, they only need to look at Watford to see that we give kids a chance in the first team.
"Ashley Young started here and is now an England international and our goalkeeper, Scott Loach, has been called up to the England squad.
"The current crop, with the likes of Marvin, Matt Whichelow and Gavin Massey, can be just as good as them. Coming through together creates a real team spirit as everyone is near enough the same age. I might be young in footballing terms but I feel an extra sense of responsibility as all the lads are younger than me."
And if Mariappa is asked for advice by any of the club's youngsters then he just has to think of what he was told by one of his principle influences — Mackay. Mariappa was on the fringes of the first-team when Mackay, who became full-time manager last June, joined the club as a player in 2005 and he was quickly taken under the Scot's wing.
He added: "I was in my first year as a pro when Malky arrived and the main thing he told me was that I had to man up. I was in the youth and reserve teams but first-team football is a man's game and he helped me to grow up.
"I looked up to and had respect for Malky as he was older and more experienced than me and now he is the manager who hasn't changed. He always had leadership ability and was very loud in the changing room, although he has had to tone his jokes down now.
"His man-management is excellent and although his relationship with some of the older players might have changed, it hasn't with me."
But could Mackay possibly lead this team into the Premier League? Surprisingly for a man who briefly studied Further Maths at AS Level after gaining 10 GCSEs, Mariappa professes not to spend too much time looking at the only table that counts — the one that shows Watford are fifth.
"We won't get carried away," he added. "Of course I want to play in the Premier League again, who wouldn't?
"But all I can say is that we've got a lot of good young players here and they're really coming of age this season."
