Five things to watch at NFL combine

With all the business happenings at the combine annually, it's no surprise the NFL moved up the start of this year's event by one day.

The main priority for teams is getting physicals and interviewing the more than 320 invited prospects. But teams will have several other boxes to mark off on their to-do lists at Lucas Oil Stadium. Along with draft prospects, teams will meet with agents to discuss contract extensions for current players, and GMs will decide which players merit the franchise tag. The competition committee will get its first look at suggested rule changes submitted by coaches and teams. Finally, the NFLPA will meet with the league to figure out the salary-cap number for 2015.

As for the prospects' schedule, player interviews with teams commence Tuesday night with the massive throng of expected reporters getting their time with prospects Wednesday. Workouts with specialists, offensive linemen and tight ends start Friday instead of the usual Saturday, and quarterbacks who decide to work out and throw will hit the field along with running backs and wide receivers Saturday. D-linemen and linebackers take over Sunday, and things conclude with defensive back workouts Monday.

Perhaps the earlier start will give teams a bit more time to properly evaluate a draft clouded in uncertainty at premium positions such as quarterback and cornerback. Despite expected temperatures hovering between minus-2 and 18 degrees, NFL business is about to heat up in Indianapolis.

Here are five things to keep an eye on at this week's scouting combine:

1. The enigmatic field of QB prospects: This is an important draft for the quarterback position. For the long-term success of the league, this draft needs to produce a few franchise quarterbacks. Since 2008, the draft has produced only eight players who could be considered franchise quarterbacks: Matt Ryan, Joe Flacco, Matthew Stafford, Cam Newton, Andy Dalton, Colin Kaepernick, Andrew Luck and Russell Wilson. The jury is still out on Ryan Tannehill and Nick Foles. The league has thrived with about 10 QB stalwarts who have kept the position afloat for the past decade, but quality young guns are needed to supplant them as age ushers the vets out of prominence.

It's not certain whether Jameis Winston, the likely No. 1 pick, will throw Saturday, but he needs to show the Tampa Bay Buccaneers he is mature enough to be counted on as a franchise guy. For Winston, nailing the interview process is far more important than anything he does on the field, as he will have to address his off-field transgressions to allay teams' concerns. Winston has the physical skills to be a franchise quarterback, but he has to show he's in shape and responsible enough to be the face of a franchise.

Marcus Mariota and Bryce Petty have to convince teams that coming from a spread offense won't be a hindrance in making the jump to the NFL. Mariota is expected to go in the top seven picks -- possibly No. 1 overall. Petty is graded as a third-rounder by some and a late first-rounder by more optimistic scouts. Folks remain undecided on the prospects of UCLA's Brett Hundley. Could a good throwing day Saturday propel him into the first round? We'll see.

With such questions about the incoming class, QB-needy teams also might scour the mostly backup-caliber free-agent market in hopes of landing a starter. Josh McCown visited Buffalo on Monday and has been contacted by seven teams. He hopes to find a new home by next week. Ryan Mallett hopes to re-sign with Houston and become the starter after showing flashes last season. And Brian Hoyer has to decide if he wants to go back to Cleveland or move on to another franchise.

2. The true value of today's running back: While the Seattle Seahawks and Dallas Cowboys displayed the merits of a strong ground game in 2014, running back is no longer viewed as a big-money position. No free-agent back received a deal worth more than $4 million per year last season, and teams haven't invested a first-round pick on a running back since 2012, when Trent Richardson went to Cleveland third overall before being jettisoned to Indianapolis the next season.

This year is considered the best running back crop since 2008. As many as a dozen could be taken in the first three rounds. Two -- Melvin Gordon of Wisconsin and Todd Gurley of Georgia -- are considered first-round talents. Gurley, in particular, will be in focus because he has to show how healthy he is following ACL surgery. Saturday's running back workouts could separate the other backs, determining whether they warrant second- or third-round grades.

3. Another great year at wide receiver: Last year's combine offered a glimpse of how great a year 2014 would be for rookie wide receivers. Most scouts and observers were amazed watching the athleticism and sure-handedness in drills. The gauntlet drill, in which a receiver must run across the field and snatch quick throws from quarterbacks, was especially remarkable. The ball hardly hit the ground.

What's impressive about the 2015 class is the abundance of size. Of the seven receivers who are potential first-rounders, Amari Cooper of Alabama is the shortest at 6-foot-1, 210 pounds, and most people still believe he will be the first receiver off the board. Among the other intriguing big-bodied, first-round-caliber talents are Kevin White of West Virginia, DeVante Parker of Louisville, Jaelen Strong of Arizona State, Dorial Green-Beckham of Oklahoma and Devin Funchess of Michigan.

4. Another sneaky-good crew of offensive linemen: Last year's offensive line class sneaked up on teams. Zack Martin and Joel Bitonio might have had the best rookie seasons from a rich class of blockers. A number of rookie centers earned starting roles and made their presence felt.

What to watch for at this combine is whether there are enough quality tackles to satisfy needy teams. Six or seven tackles could go in the first round, among them Brandon Scherff of Iowa, La'el Collins of LSU, T.J. Clemmings of Pittsburgh and Andrus Peat of Stanford. The group is talented but comes with the bonus that all but Peat were seniors. So often, that extra year of college seasoning makes for quicker adjustments into the NFL.

5. Front-seven upgrades on defense: This isn't considered a strong group of inside linebackers and safeties, and it's just average for cornerbacks. But the strength on defense is along the defensive line and at outside linebacker. With 17 or 18 teams drafting for 3-4 defenses, this year's combine is a good one to see if the draft's pass-rushers stack up against some of the expensive veteran options available in free agency.

The most interesting prospect is Danny Shelton, a 340-pound defensive tackle out of Washington who could be the next Haloti Ngata. Nebraska's Randy Gregory could go in the top three as either a 4-3 defensive end or pass-rushing linebacker in a 3-4. Defensive tackle Leonard Williams of USC is considered the best defender in the draft, so it will be interesting to see if he works out or just relies on his impressive college résumé.