With the Colts a weaker team, the team is using the matchup to give Fournette an extra week of rest. Their bye week is next week, so if the Jaguars can still pull out the victory with Chris Ivory, T.J. Yeldon, and Corey Grant in the backfield it will have been a gamble worth taking.
Fantasy-wise, Ivory is a good play today in your flex spot. The Jaguars are going to run often against a Colts defense that has given up big yards in the run game. Opposing teams have averaged 114.2 yards per game on the ground against them.
I still think the Jaguars win today, although the margin of victory will obviously be less than if they had their star running back.