Gabbert told the team's official website: "I haven't practised. That's tough when Chad has played well. My job right now is to help any way I can, to be the best teammate and the best leader I can.
"If that's to go out and give the best look [to the first-team defense] this week, that's what I'm going to do. Every day I have to get reps and practise at a high level.
"It's a week-to-week thing. It's my job to go out there and prove that I can stay healthy and prove I can play at a high level to make it hard on the coaches."
The Jaguars face the San Francisco 49ers at Wembley this Sunday.