TAMPA, Fla. (AP) - The former University of Florida running back made his NFL debut last year, appearing in two games after joining the Bucs following the close of his track and field season.

The 24-year-old, who was referred to as the fastest player in the league by coach Lovie Smith, subsequently decided to take up football full time. He is expected to see action Friday when Tampa Bay plays its preseason opener at Jacksonville, which will take its first look at rookie quarterback Blake Bortles in a game.

Demps was a member of the 2012 U.S. Olympic 4x100 relay team that won a silver medal at London.

Although he hasn't gone through a full football training camp since he was a senior in college three years ago, he and the Bucs stress the attempt to pursue a pro career is not an experiment.

''I've got a football background. I grew up playing football,'' Demps said. ''The reason I started track was to stay in shape for football. I just kind of fell in love with it having the success that I have.''

The 5-foot-7, 175-pound speedster regained his passion for the game last season, when he gained 14 yards on his only rushing attempt, had three pass receptions for 21 yards and averaged 23.3 yards per return on four kickoffs against Arizona and Philadelphia.

Tampa Bay's depth chart for Friday night lists him as the fifth running back behind Doug Martin, Bobby Rainey, rookie Charles Sims and Mike James.

Smith cautions it's far too early to predict how a player with Demps' potential might fit into plans for a team that ranked last in passing and total offense in 2013.

''You hear that title fastest man in the NFL. You search for ways to utilize him,'' Smith said, adding it's difficult to not notice fans ''ooh-ing and ahh-ing'' when Demps lines up in the slot as a potential receiver or settles under kickoffs during practice.

''Sometimes you get a track athlete, they'd rather work out before you put pads on,'' the coach added. ''That's not the case with Jeff. Jeff will let you know he is a football player.''

Demps averaged 6.7 yards per carry in rushing for 2,470 yards and 23 touchdowns in four seasons at Florida from 2008-11. He had 57 receptions for 481 yards and averaged over 28 yards on kickoff returns, while also helping the Gators win a national championship.

He initially entered NFL as an undrafted free agent with New England in 2012, appearing in two preseason games before being placed on injured reserve.

Unable to obtain a full-time commitment from Demps, the Patriots traded him to Tampa Bay in exchange for LeGarrette Blount in April 2013.

Demps joined the Bucs in September, making his debut against the Cardinals and playing a limited role the following game against the Eagles. He inactive the next three games, then spent the final eight weeks of the season on injured reserve (groin).

Being around football again for an extended period, though, rekindled his enthusiasm.

''I still love track and field, no doubt about that. But I think it's for me this year to just focus on football and get better at that,'' Demps said.

''I don't know if it was because I was away ... or injuries, but it's kind of like I had lost the love for the game,'' he added. ''When I came in for those weeks and got to practice with the guys, the atmosphere felt like college and I felt that passion for it again. It sparked everything, and I said let me try to give this a full shot and see what I can do with it.''

Smith likes what he's seen so far.

''It's early. What you do is you continue to put players in a position to make plays,'' the coach said. ''Jeff seems to get noticed just about every day. It's tough competition. I like all of our running backs. But he brings something that's a little unique, so we'll see.''

Chad Henne will start at quarterback for the Jaguars, who plan to play their starters for about a quarter.

Bortles, the third overall pick in the draft, has not taken any snaps with the first-team offense during training camp. Coach Gus Bradley doesn't anticipate that changing Friday night.

''Right now we're looking at the second quarter, and we'll see how it goes in the third quarter,'' Bradley said. ''We'd like to get him some extended reps.''