Coach Gus Bradley was asked whether Robinson was running plays as a true quarterback or practicing the Wildcat formation, but he declined to say.
"I'm not going to say," Bradley told reporters, according to the team's website, which said he was laughing. "But that's tough on defense, because what is he?"
The Jaguars have four quarterbacks on their roster, led by incumbent starter Blaine Gabbert and veteran Chad Henne. Jordan Rodgers had sports hernia surgery this week and will be sidelined until training camp. Undrafted rookie Matt Scott rounds out the group.
Robinson started 37 games at Michigan, including 35 at quarterback, and set the NCAA record for career rushing yards (4,495) by a quarterback. He agreed to move to receiver, running back or even cornerback before the draft.
Robinson completed 57 percent of his passes for 6,250 yards, with 49 touchdowns and 39 interceptions, in four years at Michigan. Nicknamed "Shoelace" because he plays with his laces untied, Robinson added 42 touchdowns on the ground. He also caught three passes and returned two punts.
He recently told Yahoo! Sports that he misses playing quarterback but is just happy to be playing football.
"Of course you miss it, but it's still football," Robinson told the website.
Meanwhile, the Jaguars on Thursday released special teams ace Montell Owens after seven seasons. The Jaguars want to get younger, so the move was hardly a surprise.
Owens, a two-time Pro Bowler, is the latest veteran to leave the rebuilding Jaguars, joining a list that includes cornerback Rashean Mathis, linebacker Daryl Smith and fullback Greg Jones. The team filled one of two open roster spots by signing first-year center Dan Gerberry, who tried out during a voluntary veteran minicamp last month.
Information from The Associated Press was used in this report.