USC center Marcus Martin, considered one of the top two players at his position in the draft, has met with Carolina, New Orleans and Philadelphia.
Neither is seen as a first-rounder, though there always is a possibility that one could sneak into the first round.
There have been just nine centers drafted in the first round this century. Wisconsin's Travis Frederick was a surprise first-rounder last season, by Dallas, and played well as a rookie. He was the first center taken in the first round since 2010. There have been 16 second-round centers this century, and Martin and Richburg seem likely to go in that round.
Center wouldn't appear to be a high priority for Carolina, which has Ryan Kalil as its starter, or Philadelphia, which has Jason Kelce, but New Orleans definitely could be in the market for one. The Saints pick 27th in the first round and 26th in the second round (58th overall). Baltimore, New England and San Francisco are other teams that could be looking for a center, and the Ravens are the only one of the three that picks before the Saints in the second round.
Martin (6-foot-3, 320 pounds) left USC after his junior season. He started 33 games in his Trojans career and started at guard in his first two seasons. Still, center is his best position. He missed his final college game, a Las Vegas Bowl win over Fresno State, because of a dislocated kneecap. He appeared fully healthy when running the 40-yard dash twice and doing position-specific drills at USC's pro day March 12.