Leicester captain Jamie Vardy stopped play by blowing the referee's whistle, which was attached to Webb's wrist.
Webb received medical attention and got to his feet before being replaced by the fourth official.
The incident occurred during Vardy's final season with Leicester City after 13 years at the club. He scored his 144th Premier League goal in the match.
The lengthy delay for the referee change resulted in 12 minutes of added time in the first half.