JACKSONVILLE – We turn our focus now to the familiar.

We're now less than two weeks from the real stuff, and with that time drawing near, we move on in this weekly look ahead to Jaguars 2015 Training Camp to a topic that very much lacks newness.

We've already looked at breakout players. And rookies. And incoming free agents. But the reality for the Jaguars is success in 2015 may depend as much on players returning, developing and improving as it does on any newcomers.

Yes, more than a quarter of the roster may be recently-signed free agents and draft selections …

But that means nearly three quarters of the roster will be returning players – and not all of those returners necessarily need to break out or have headline-grabbing impact. Some just need to mature and play their roles – of course, in so doing they could qualify as breakout players, too.

Here's a look at the top five returning players to watch in 2015:

1.Luke Joeckel.With the exception of quarterback Blake Bortles, no Jaguars player may be under more scrutiny entering 2015. The No. 2 overall selection in the 2013 NFL Draft, Joeckel missed the final 11 games of his rookie season with a broken ankle. That cost him experience, and the rehabilitation from that injury an offseason ago cost him valuable strengthening and conditioning time. That hurt him last season, and Joeckel has been open and forthright about his need to improve this season after struggling at times in his first full season as an NFL left tackle. Joeckel last season didn't play as poorly as many observers believed, but the improvement of the Jaguars' offensive line as a whole is one of the critical storylines entering 2015. Within that unit, Joeckel's development is the top storyline.

2.Chris Clemons.It's not accurate to say Clemons needs to develop, exactly. Entering his 13th NFL season, that may or may not be possible. But the Jaguars absolutely need Clemons to at least match his effectiveness last season when he had eight sacks after signing with the team as a free agent. Clemons was critical anyway, but the loss of rookie pass rusher Dante Fowler Jr. – the No. 3 overall selection in the 2015 NFL Draft – for the season added to his importance. Clemons said during June minicamp that he was 17 pounds lighter than last season, meaning he weighed 248 pounds. He believes the weight loss will help him improve significantly this season. That's needed, because while Andre Branch, Ryan Davis and Chris Smith add depth, Clemons played the vast majority of the Leo snaps last season; the Jaguars need his pass-rushing impact.

3.Johnathan Cyprien.If there is a defensive player in a similar situation to Joeckel, it's Cyprien. A second-round selection in the 2013 NFL Draft – the first for General Manager David Caldwell and Head Coach Gus Bradley – Cyprien was expected to be a core player and building block. Like Joeckel, Cyprien has shown potential but also like Joeckel he has been more inconsistent than is ideal. The hope is the Jaguars' additions at free safety – where rookie James Sample and veteran free agent Sergio Brown will compete – will help Cyprien. Cyprien and the coaching staff agreed that he appeared to be playing more quickly and with less hesitation during the offseason program. That needs to carry over into training camp and the regular season.

4.Toby Gerhart.This isn't necessarily a "have-to" entry; the Jaguars are deep enough at the position that aside from rookie T.J. Yeldon, no player is absolutely irreplaceable. But Gerhart enters training camp in a position to provide the Jaguars very good depth – and productivity from the backup position they haven't had in some time. Many observers wrote Gerhart off with the Jaguars last season when he struggled after signing with the team as an unrestricted free agent. But Gerhart was productive in a limited role late in the season and much of his early struggles could be attributed to a foot injury in the regular-season opener. If Gerhart is the third-down/pass receiving threat he showed he could be late in the season, the Jaguars could improve significantly at running back.

5.Sen'Derrick Marks.This entry is about injury far more than ability. Marks has been the Jaguars' best defensive player the past two seasons and led the team with 8.5 sacks last season. But he sustained a torn anterior cruciate ligament in a season-ending loss at Houston and has spent the offseason rehabilitating that injury. Marks' stance is that he is focused on being ready for the regular-season opener against Carolina September 13. That's eight months out from surgery, so that's a lofty goal. Whatever Marks' season-opening status, how quickly he can return – and more importantly, return to a near-Pro Bowl status – will be critical to the Jaguars' defense continuing the progress it showed last season.