World number one Luke Donald has added the Children Miracle Network Classic to his schedule as he bids to top the PGA Tour money list.
He currently tops both the PGA and European Tour money lists but is under increasing pressure from Simpson.
Donald is currently $68,971 (£43,602) ahead of Simpson as he bids to become the first player to top both the PGA Tour and European Tour earnings in the same season.
It could also be the first time that the PGA Tour money title comes down to the final tournament of the season.
The Children Miracle Network Classic gets underway at the Walt Disney World Resort on Thursday, October 20.