It is very hard to win in the NFL without three very good cornerbacks. In recent years, teams play what is called a "slot corner" to match up with plethora of slot pass catchers populating the NFL. In 2012, some teams played three cornerbacks on more than 50 percent of their downs. It also used to be that cornerbacks were converted wide receivers who lacked good hands. However, don't be surprised if the Arizona Cardinals play cornerback Patrick Peterson as a wide receiver this season, as he has practiced at that position in training camp, thus displaying the athletic abilities of the modern corner.

-- Gil Brandt (follow on Twitter @gil_brandt)

The 5-foot-9 3/8, 175-pound Verrett lacks the ideal height and weight for the position, but makes up for it with great ball skills and very good speed (timed at 4.4 seconds in the 40-yard dash). He led the Horned Frogs with six interceptions and 16 pass breakups in 2012, and was also the team's fourth-leading tackler with 63 total tackles. Watch his play against West Virginia and quarterback Geno Smith last season to get an idea of how good Verrett is (he picked off a pass, and then blocked a field goal that helped TCU defeat WVU in double overtime). (Mandatory Credit: Jerome Miron-USA TODAY Sports)

Dennard (5-foot-11 3/4, 190 pounds) was a first-team, All-Big Ten selection in 2012. Dennard -- who runs a 4.5-second 40-yard dash -- had three interceptions and seven pass breakups in 2012. Dennard registered two interceptions -- including one returned for a touchdown -- in the Spartans' 33-30 triple-overtime win over Georgia in the 2012 Outback Bowl. He has very good ball skills and will become a big-time player. (Mandatory Credit: Mike Carter-USA TODAY Sports)

Colvin (6-foot-0 1/2, 185 pounds) played and started at safety in 2011 before moving to cornerback for the 2012 season. He was the third-leading tackler on the team, and recorded four interceptions and 11 pass breakups. Colvin -- who sports a 4.5-second 40-yard dash -- has good cover skills and is a physical player. (AP Photo/Sue Ogrocki)

The 6-foot-0 1/2, 200-pound Gilbert was an outstanding kickoff returner last season, averaging 25.8 yards per return with a touchdown. Gilbert -- who runs the 40 in 4.5 seconds -- is a very physical cornerback who had 60 tackles and nine pass breakups last season. However, he did not have an interception, so NFL teams are left wondering if Gilbert lacks the ball skills necessary for the position. (AP Photo/Eric Gay)

Washington (5-foot-11 5/8, 186 pounds) runs the 40-yard dash in 4.5 seconds. Every year it seems a defensive back comes out of a non-major Louisiana school; the Chicago Bears' Charles Tillman and the Pittsburgh Steelers' Ike Taylor are from Louisiana-Lafayette, the Green Bay Packers' Tramon Williams went to Louisiana Tech, for example. Washington is that quality Louisiana small-college cornerback this season. (AP Photo/ Butch Dill)

Exum (5-foot-10 5/8, 218 pounds) decided to stay in school for his senior season, but tore his ACL in January while playing pick-up basketball. He would have cracked the top five on this list if it wasn't for that injury. Exum -- who runs a 4.5-second 40-yard dash -- finished 2012 with five interceptions and 16 pass breakups. (Mandatory Credit: Douglas Jones-USA TODAY Sports)

The 6-foot-1, 205-pound Desir -- who runs a 4.57-second 40-yard dash -- is a small-school prospect who has the size and speed NFL teams are looking for in a cornerback. (Credit: Don Adams Jr.)