Gabbert started the 2012 campaign as the first-choice QB, but an injury allowed his teammate to come into the side for the final six games of the season.
Offensive coordinator Jedd Fisch told the team's website: "We have two guys competing as hard as they possibly can to put themselves in position to be the starting quarterback.
"I think they need to have tunnel vision. I think they need to focus on what they can control and not focus on really anything other than that."
The Jaguars will play their week eight home game against the San Francisco 49ers at Wembley Stadium.