Sanchez, Harvin have plenty to prove

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Todd McShay breaks down the players who have the most to gain and tells you small-school prospects to know, who will be the fastest player in this year's combine and what kind of schedule the players have this week. To see this and more, become an ESPN Insider.Insider

The 2009 NFL scouting combine is a place where draft stocks can rise or fall rather quickly. One bad 40-yard dash time could send a player tumbling down, while one great interview with a coach and general manager could send a player soaring up the draft board. It's a job interview like no other in the country.

As the players make their final preparations, here's an early look at some prospects who have the most on the line:

Five under the most pressure to perform

1. Mark Sanchez, QB, USC
There are a few areas Sanchez needs to address this weekend to prevent his stock from dropping. First, he needs to interview extremely well. In particular, he needs to overcome the concerns that teams will have regarding his inexperience when they put him in front of the chalkboard. Second, he needs to erase doubts about his long-term durability by passing his medical exams, but whether he does is out of his hands. Third, Sanchez needs to show adequate arm strength during passing drills.

2. Percy Harvin, WR, Florida
Few prospects will be scrutinized more during medical exams than Harvin, who has a history of leg, ankle and foot injuries. Doctors will search to learn whether all the past problems and procedures could create concern for his long-term NFL future. And if Harvin chooses to run, he needs to verify the blazing speed seen on game tape by clocking a 40-yard dash in less than 4.4 seconds.

3. Vontae Davis, CB, Illinois
There are some concerns about Davis. He did not perform up to expectations as a junior in 2008, his focus is inconsistent and his technique needs polishing. But make no mistake, Davis has phenomenal talent. He possesses good size, fluid hips and elite closing burst. To overcome the concerns about him, Davis needs to put on a show in Indy much like his brother Vernon Davis did in 2006.

4. James Laurinaitis, ILB, Ohio State
Scouts were anything but impressed with Laurinaitis' decision to not play in the Senior Bowl, so now he's playing catch-up. First, he needs to convince NFL decision-makers he had a good reason not to attend the all-star game. Then he needs to exceed what are mediocre expectations throughout the physical portion of the four-day interview. Even if he does both, Laurinaitis likely would secure a spot only in the bottom half of the first round.

5. Shonn Greene, RB, Iowa
Greene's production in 2008 was mind-boggling for a young man who was delivering furniture a season earlier. There's no questioning Greene's power and instincts as a runner. However, to lock down a spot, Greene must impress in the interview room on Day 1, then run a respectable 40 time (in the low 4.6-second range) and catch the ball well during passing drills.