INDIANAPOLIS (AP) Football fans see the NFL's annual scouting combine as merely a numbers game that comes down to the times, jumps and drills they witness on television.

NFL executives are more interested in getting behind-the-scenes answers through medical checks and personal interviews.

It's a delicate balancing act.

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''When we finally get the measurables on the underclassmen, when we find out where they are medically, where they are physically, where they are with the interviews, then we'll have a better idea (of where they rank),'' ESPN draft analyst Mel Kiper Jr. said on a conference call with reporters Monday, one day before the first players begin arriving in Indianapolis.

Sure, the workouts matter.

Chris Johnson's draft skyrocketed after breaking the combine record with a 4.24-second 40-yard dash in 2008. Cornerback Byron Jones jumped up draft boards - literally - after a record-breaking broad jump of 12 feet, 3 inches last February. Both wound up being first-round picks.

The ramifications for those who underperform or sit out can be damaging, too.

In 2014, quarterback Teddy Bridgewater decided not to throw in Indy, then had a less-than-stellar pro day at Louisville. The result: A player thought to be in the running as the No. 1 overall pick was still available at the end of the first round, a plummet that cost Bridgewater big bucks.

He led the Minnesota Vikings to the 2015 NFC North title this season.

The most costly mistakes come when teams miss red flags.

Two years after Cleveland took Heisman Trophy-winning quarterback Johnny Manziel, his off-the-field problems have led to wide speculation the Browns will release their once future franchise quarterback. San Diego and Oakland found themselves in similar dilemmas with Ryan Leaf and JaMarcus Russell through the years.

That's why longtime NFL decision-makers, such as Hall of Fame executive Bill Polian, insist the most essential component during combine week is what nobody actually sees - real answers to some basic questions from the more than 300 players who show up each February, especially from players who have histories of injuries or off-the-field troubles.

Some other things to watch this week:

MEDICAL TESTS: Nobody may have more at stake this week than two of this year's top-rated linebackers, UCLA's Myles Jack and Notre Dame's Jaylon Smith. Both finished their seasons with torn knee ligaments and while both could be taken among the first 15 picks, this week will be the first time NFL doctors have a real chance to get a peek at their recoveries.

PERSONNEL MOVES: The next big players in the NFL are likely to take a backseat to some of the current biggest names in the league during the first two days of the combine, when coaches and general managers typically provide offseason updates. With free agency looming, expect to hear plenty about the futures of players such as Robert Griffin III, Peyton Manning and Manziel among others.

RULES CHANGES: The NFL's competition committee won't take any votes this week. But it will talk about potential proposals at the March owners' meetings in Boca Raton, Florida. Hot topics this year could include a more stringent definition of what's considered a catch, and whether players who receive multiple personal fouls in a game should be ejected.

BUYER BEWARE: Every year, some player turns heads with big numbers, only to fail miserably. Past workout warriors on this list include Brent Fullwood, Mike Mamula and Tony Mandarich. One thing that is almost certain is it will happen again to some team this year.

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