Striker Steve Brooker came off the bench to score an equaliser with his first touch in a Doncaster shirt to earn his side a point against Watford.
Tommy Smith put the Hornets ahead when he converted Tamas Priskin's cross.
But Brooker, who joined Doncaster from Bristol City on Thursday, connected with John Spicer's cross to level the score six minutes after coming on.
The visitors came close to stealing a win when James Coppinger's drive was tipped around the post.
Watford manager Brendan Rodgers: "In the first half we showed some very, very good moments and it led to the goal which was a very, very good goal.
"At half-time I'm thinking there's a game that we can go on and do well and do better in the second half, but sometimes it happens naturally and you get caught deep and it's very, very difficult to get out.
"I thought in the second half it was very difficult for us and so overall at 1-1 I was pleased."
Doncaster manager Sean O'Driscoll: "I thought we created enough chances to win the game.
"The longer the game went on the stronger we got, but it was a sloppy goal we gave away from our throw-in and it should have been cleared.
"Their manager made changes and we were wondering how they would play. In the first 20 minutes both sides were sort of looking at each other, seeing what they could do, they got the goal and we had to respond in the second half which I thought we did."
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