ENGLEWOOD, Colo. -- A plethora of aerial weapons at Peyton Manning's disposal doesn't mean the running game will be ignored. To the contrary, upgrading the ground game was one of the Broncos' offseason priorities, although unlike with other positions, the path to improvement at running back typically means getting younger and fresher.

And that leads into what could be the most compelling competition of training camp: the battle to be the Broncos' starting running back. Following the June release of Willis McGahee, the race is likely to come down to three running backs in whom the Broncos invested high draft picks the last five years: 2013 second-rounder Montee Ball, 2012 third-rounder Ronnie Hillman and 2009 first-rounder Knowshon Moreno.

But the starter might not be the one who gets the most carries on a game-by-game basis. That's the nature of a platoon system, which John Fox often used in Carolina, and which offensive coordinator Adam Gase indicated would be in play this year.

"Coach Fox has always been great mixing in the multiple backfields and using different guys. He did it in Carolina, and that's what we're looking to [do]. We'll do the same thing here," Gase said in May.

In Carolina, Fox's running back platoons usually saw the more experienced runner start, e.g. Stephen Davis over DeShaun Foster, Foster over DeAngelo Williams and Williams over Jonathan Stewart. But the primary ballcarrier was often determined by game situations, matchups or simply who had the hot hand. 

Substitutions were made after several plays or between possessions. That wasn't a necessity with the more deliberate tempo the Panthers used during most of Fox's tenure with them, but will be if Gase wants the offense to go as fast as he intends.

"A guy could be on the field five or six plays, especially with us being in no-huddle, so you don't have guys running back and forth to where it's two [plays] here, three [plays] here," Gase said. "We need guys to stay on the field for longer stretches of time. That's a good thing, to have a deeper running back crew like we have."

Hillman has burst in the open field. Moreno proved he could handle a grind-it-out, between-the-tackles role after replacing McGahee as the primary ballcarrier late last season. Ball was extraordinarily durable at Wisconsin, but likely won't face workloads as massive as he did there. He had at least 30 touches in eight of his last 18 games -- and didn't miss a game to injury in the process.

"He has great vision. I never really saw him take the massive shot," Gase said. "He did a great job of being able to avoid the big hit. I don't think that's going to affect him. I think what he does is carry the ball. That's his strong suit."

But to be the primary running back, your strength must also include blocking. While ground production is vital, the season could rest on a blitz pickup to keep Manning upright. Whoever earns the job will be the one who, above all, reads blitzes the quickest and prevents the 37-year-old quarterback from taking the one hit that could rearrange the Broncos' season.

Since blocking will be crucial, the X-factors in the running back corps could be Lance Ball and Jacob Hester, the jacks-of-all-trades. Hester is a particularly intriguing option based on how Gase used him during OTAs.

"To be able to play halfback, fullback -- we throw him on the wing every once in a while, we can spread him out," Gase said. "is versatility is huge for us because we can do some things. It should help in our short yardage, goal line, four-minute packages. 

"It's been a big point of emphasis this offseason to figure out how we get him on the field and use him a little more, whether he's playing tailback, fullback, an F-tight end and H-back. We're going to try to use him as many ways as possible."

If he can move around that much and be a capable threat at each spot, he can change a formation without changing on-field personnel, allowing the Broncos to give different looks while maintaining a quick tempo and minimizing substitutions. He could also help keep the primary backs fresh --  whoever they turn out to be.

THE RUNNING BACKS: THE BASICS

Ronnie Hillman: As his weight hovered around 180 pounds last season,  Hillman was regarded more as an open-field, change-of-pace back. If he ends up around 200 pounds, he'll be at the weight he held going into the 2012 scouting combine. The key is being able to keep it on during the season. "Hopefully it gives me about five more yards after contact, but you can't tell right now," Hillman said. Once preseason comes and I starting getting in pads and picking up these blitzes when they really come, I'll be able to tell a lot more."

Montee Ball: He appears to have the vision, acceleration and decisive first cut to be a stellar pro running back. But he knows blocking will determine his playing time, and in addition to studying the playbook, he plans to use his college experience blocking for Seahawks Pro Bowler Russell Wilson as a building block. "Our offensive coordinator (Paul Chryst, now Pitt's head coach) gave Russell the green light to change the calls at the line of scrimmage," Ball said. "I have a lot of plays with Russell where I had to really pass protect him."

Knowshon Moreno: He had back-to-back 100-yard games for the first time in his career last year with 119 yards at Oakland and 115 at Baltimore. But his production tailed off after that, and his per-carry averages for the last three games of the season (including the playoff loss) were 3.5, 2.9 and 3.2. He's also in a contract year and for the second consecutive offseason, was limited in his practice work because of an injury rehabilitation.

Jacob Hester: There are no fullbacks listed on the roster after Chris Gronkowski was not brought back. The 5-foot-11, 225-pound Hester is the closest thing to one, having worked there in San Diego and briefly after joining the Broncos last year. But if he sticks on the roster, it won't be solely as a fullback; while they kept a pure fullback last year, none are currently on the roster.

Lance Ball: The last three years, no Broncos running back has worn as many hats as Lance Ball, who's worked in multiple special-teams roles in addition to his work on offense. He could be grappling with Hester for a spot, as both share a primary attribute (versatility) and are of similar size.

Jeremiah Johnson: He's always provided a spark during training camp, and only Moreno has more rushing yardage for the Broncos in the last two seasons than Johnson, with 127 yards on 33 carries and a score in that span. But he's spent parts of three seasons on the Broncos' practice squad, which means he's at the point of his career where it's the 53-man roster or bust.

C.J. Anderson: The only rookie in the position group, Anderson is the shortest (5-foot-8), but also the second-heaviest, just one pound shy of Hester. Anderson averaged 6.3 yards per carry last year at California and could become a practice-squad insurance policy if he shows the same explosion this summer.