OverviewThe center position is as bad as it’s been in years, with only a few draftable prospects. Wisconsin’s Travis Frederick and Alabama’s Barrett Jones are the top center prospects and likely second- or third-rounders. Tackle and guard both are strong at the top. The top three offensive tackles — Texas A&M’s Luke Joeckel, Central Michigan’s Eric Fisher and Oklahoma’s Lane Johnson — will go in the top 12. The top two guards — Alabama’s Chance Warmack and North Carolina’s Jonathan Cooper — are projected as top choices, too, possibly both top-10 picks. But neither position offers good depth.Cowboys’ needsThe Cowboys have spent a lot on their offensive line the past two off-seasons. They signed Doug Free to a four-year, $32 million deal with $17 million guaranteed before the start of the 2011 season to be their left tackle. He now plays right tackle and didn’t play it very well last season with 13 penalties, including five holds, and seven sacks allowed, according to STATS, Inc. They drafted Tyron Smith with a first-round pick in 2011 and gave him a guaranteed four-year, $12.5 million deal. He has become the team’s best lineman and a solid LT. The Cowboys tried to shore up the guard positions last off-season with the signings of Mackenzy Bernadeau and Nate Livings. They signed Bernadeau to a four-year, $11.5 million deal with $3.25 million in the form of a signing bonus. Livings signed a five-year, $18.75 million deal that included $3.5 million to sign. The total guaranteed money was $6.2 million. Yet, the Cowboys are back looking to shore up the middle of their offensive line. Bernadeau could be tried at center. He started two games there in 2012. But it is a good bet the Cowboys use an early pick on an offensive lineman.Top three OT Luke Joeckel, Texas A&M, 6-6, 306, 5.25. The Arlington product started every game at LT in his three seasons. Eric Fisher, Central Michigan, 6-7, 306, 5.03. He made 28 career starts at LT, four at RT and two at RG. Lane Johnson, Oklahoma, 6-6, 303, 4.69. With 35-inch arms and his ability to play either side, the Groveton High and Kilgore College product will be an early pick.Top three C/G Chance Warmack, Alabama, 6-2, 317, 5.49. He had 39 career starts at LG, and in 2012, he had 37 pancake blocks only two penalties in 732 snaps. Jonathan Cooper, North Carolina, 6-2, 311, 5.06. He had 47 career starts, and in 2012, he played every snap, graded out at 90 percent and had 18 pancakes. Larry Warford, Kentucky, 6-3, 332, 5.56. He played in 47 games, with 37 consecutive starts, and in 2012, he did not allow a sack in earning All-America honors.Sleeper Garrett Gilkey, OT, Chadron State, 6-6, 318, 5.29. The top Division II lineman earned a draft selection with his performance in the Senior Bowl.Top Texas ties Blaize Foltz, OG/C, TCU, 6-4, 324, 5.35. He could be a seventh-round choice after making 26 starts at RG over past two seasons.Source: Heights, weights and 40 times were compiled from NFL Draft Scout.