The Tottenham Hotspur midfielder has moved to Brentford on a season-long loan deal, and Warburton, who guided the Bees to promotion last year, has revealed that he has kept an eye on the development of the 21-year-old for a number of seasons.
The 51-year-old told the club's official website: "Alex is a player that I have watched for many years. He is very good tactically and technically, with excellent dead ball delivery.
"Alex will add to the quality in our squad, which is taking shape nicely ahead of the start of the season."
Pritchard netted eight times in 44 appearances during a loan spell with Swindon Town last year.