PITTSBURGH -- Cornerback may be the Pittsburgh Steelers' biggest need in this year’s draft, and ESPN draft analyst Mel Kiper Jr. has the Steelers landing the top one on his board.

Kiper has the Steelers taking Oklahoma State’s Justin Gilbert with the 15th overall pick, changing his selection from Notre Dame defensive tackle Louis Nix III.

Kiper had the Steelers picking Nix in his first two mock drafts.

Kiper has Gilbert rated the 14th best player in the draft and the top one at what is considered a deep position this year.

The 6-foot, 202-pound Gilbert has good size and excellent speed. He ran the 40-yard dash in a blazing 4.38 seconds at the NFL scouting combine last month.

Gilbert’s showing in Indianapolis bolstered his stock following a season in which he intercepted seven passes, recorded 42 tackles and was a finalist for the Jim Thorpe Award, which is given annually to the top defensive back in college football.

Here is what Kiper wrote about Gilbert, who could also be a return man in the NFL:

His athlete credentials are strong. On the field, he combines short-area quickness to adjust to routes and open-field speed to run with (or past) any receiver. He has enough size and strength to redirect routes at the line and can then flip his hips and run with anybody; he rarely allows much separation. Good ball skills and hands are evident both in coverage and the return game. Given the need at the position, it's not out of the question that he lands in the top 10.

The Steelers have not used a first-round pick on a cornerback since 1997 when they selected Chad Scott 24th overall but they need to draft at least two players at the position this year.

Ike Taylor agreed to a restructured deal earlier this week but he is not expected to play for the Steelers beyond 2014. William Gay and Cortez Allen are the only other experienced cornerbacks on the roster, and the former turned 29 in January.

Gilbert or Michigan State's Darqueze Dennard would make a lot of sense for the Steelers with their first pick in the draft.