NFL prospects gathered in Indianapolis today for the beginning of the annual NFL Scouting Combine in Lucas Oil Stadium.

Players gather at the combine every year to be evaluated physically and mentally by coaches, general managers, and scouts from various NFL teams, as well as members of the media.

Some of the more notable players arriving in Indianapolis today include University of Southern California OT Matt Kalil, Iowa OT Riley Reiff, and Stanford OT Jonathan Martin, all of whom could go in the early picks of the NFL draft.

The first day of the combine will be fairly quiet, as only offensive linemen, tight ends, and special teams players will have arrived. Quarterbacks, running backs, and wide receivers will arrive on day two, defensive linemen and linebackers will arrive on day three, and defensive backs will arrive on day four.

Each group will stay for four days and undergo a battery of tests, lasting until the defensive backs leave the combine on Feb. 28.

The combine is expected to really heat up on day two, when high-profile quarterbacks Andrew Luck and Robert Griffin III arrive. Luck, from Stanford, is expected to go with the first overall pick of the draft, while Griffin, from Baylor, is expected to follow soon after.

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Still, those who want to watch Luck and Griffin face off may be forced to wait. In a press conference earlier this week, Griffin said he would be attending the combine, but he probably would not throw any passes.

"It would be foolish to say it's even a fair and equitable environment for throwing," Griffin said. "When you show up in a game, you're never going in without a game plan. It's a disadvantage to throw when you have no idea of the rhythm that you will have with your receivers."

"I'll decide when I get there. I'll do the other tests and see how it goes," Griffin added.

Luck has also not decided whether or not he will throw at the combine, but he has been preparing with George Whitfield, who trained current Carolina Panthers QB and last year's first overall pick, Cam Newton.

Whitfield told Joe Schad of ESPN that Luck is still undecided about whether or not he'll throw, but the young QB is prepared either way.

Common tests for players at the combine include the 40-yard dash, 225-lb, bench press repetitions, vertical jump, broad jump, and various position specific drills. Players will also sit down for interviews with team officials, as well as a drug test and the Wonderlic Cognitive Ability Test.