Gabbert's position came under threat last season from Chad Henne, who replaced Gabbert in the side when he was ruled out with a shoulder injury.
However, the 23-year-old has impressed coach Gus Bradley enough during pre-season to hand him a start against the Miami Dolphins on Friday.
"I think that he's really shown a lot of poise. I think he handles situations that have been presented to him in practice," The AP quotes Gabbert as saying.
"They both have done some really good things, both have made some really good progress. Now, are they there yet? No, and I hope they would both answer it the same way.
"We just felt like with Blaine, with what he's done the last couple days in practice and how he's responded, we decided to give him the nod."
The Jaguars will begin their regular season against the Kansas City Chiefs on September 8.