The 20-year-old, starting his second loan spell at Vicarage Road, beat Steve Simonsen with a low right-footed drive after Carl Hoefkens' botched clearance had allowed Darius Henderson to set the winger up.
However, the Hornets, who won 3-0 at the Britannia Stadium earlier in the season, didn't have it all their own way and Luke Chadwick twice spurned good opportunities to equalise.
Both sides set out their attacking stall from the first whistle, but decent goalmouth opportunities were at a premium, although Watford created what clear chances there were.
First Simonsen had to be alert to keep out a low Anthony McNamee shot which bounced up in front of him, and then the Stoke keeper did even better, diving full length to his left to push behind a stinging 25-yard effort from Marlon King.
But the chances started to come at both ends when the action resumed after the break, with Stoke having the first opening as Marlon Broomes flashed an angled shot on the turn wide.
Watford skipper Gavin Mahon then tested Simonsen with a well-struck attempt, but the visitors went close again when Kevin Harper turned Jay DeMerit but dragged his shot wide.
After Watford took the lead former Stoke keeper Ben Foster denied his old club when he did well to keep out a Chadwick shot. The former West Ham winger, who turned down a move to Watford to stay with the Potters, then had another clear sight of goal but blazed badly over when well placed in the area.
City suffered a further blow when experienced professional Gerry Taggart was sent from the dugout following an altercation with fourth official Andy Woolmer.
After his dismissal Watford again took charge of the contest and missed a couple of opportunities to add to their tally in the closing stages.
Mahon almost scored a bizarre goal with 10 minutes remaining, when he got the better of a block tackle with Broomes and the ball cannoned out of play off the outside of the post and Eagles nearly doubled his tally late on when a fine cross from substitute Hameur Bouazza sat up perfectly for the youngster, but he fired badly over from 10 yards out.