The striker got across his marker to meet Dwight McNeil's splendid cross at the near post to guide a header past Ben Foster in the 73rd minute.
The result lifted the Clarets into 11th spot in the Premier League and left the Hornets scrapping for their lives at the bottom end of the table.
Here are the player ratings...
5. Ben Mee 7
Leading the side by example. The skipper made a number of key interventions throughout, including several challenges inside the area that had to be perfectly timed. Gave everything for the cause, which resulted in a deserved clean sheet.
6. Josh Brownhill 6
You can already see that the midfielder has bought into everything boss Sean Dyche has built. Works hard to get behind the ball and both cover and protect his full back. Had a big hand in the winner when winning the ball in the middle of the park.
7. Dwight McNeil 7
Dipped in and out of the game, but showed his quality when getting on the ball. A number of teasing crosses proved problematic for the Watford defence and he clocked up his sixth assist of the season when delivering for Rodriguez.
8. Ashley Westwood 7
Broke up play well to prevent the Hornets from playing through the middle, pressed the opposition hard, always looked to get on the ball to influence play and unlocked the Watford rearguard with a number of passes over the top.