The Green Bay Packers took another step in bolstering their secondary Sunday by selecting San Diego State defensive back Marviel Underwood with their first pick of the fourth round, the 115th overall selection.

A 5-foot-10, 205-pound burner with 3.38 speed, Underwood is a player with one of the Packers' most coveted traits: versatility.

"He can play strong (safety), free (safety) or corner," said Packers West Coast scout Sam Seale. "From what we're told, (coordinator Jim Bates') defense is going to be blitzing, and we need safeties that you don't have to take out of the game; they can just stay in the game and play corner, and that's what he can do."

According to Bates, Underwood will start out at safety, his primary position in college and also the place where the Packers' lineup has the biggest hole after the departure of Pro Bowler Darren Sharper to the Minnesota Vikings.

In three years as the starting free safety for the Aztecs, Underwood tallied 209 tackles and seven interceptions. Last season against Michigan he had seven tackles and also ripped a ball away from standout receiver Braylon Edwards, who went to the Cleveland Browns with the third overall pick of the draft.

Reggie McKenzie, the Packers' director of pro personnel, called Underwood a solid tackler who can "flat-out run" and is "tough as nails."

Underwood was the second of three defensive backs the Packers acquired in the 2005 draft -- they took Bethune-Cookman's Nick Collins in the second round and former Oklahoma corner Michael Hawkins in the fifth round -- but there's a feeling in Green Bay that he may be the most ready to contribute immediately.

"Underwood, in a lot of our minds upstairs, was maybe the most complete safety on the board," Bates said. "After (Georgia's Thomas) Davis was gone (14th overall to Carolina), after (Michigan's) Marlin Jackson was gone (29th overall to Indianapolis), he started fitting right into the picture.

"He reminded us a lot of Brock Marion. He has that type of athleticism and is a good open-field, sure tackler and played smart ... It's going to be a real battle for positions, which is really exciting."

In addition to the rookies, the Packers also have on their roster veterans Eric Little (8 seasons), Mark Roman (6), Arturo Freeman (6), Todd Franz (4) and Julius Curry (1).

Underwood is eager to get the battle started. The Packers roster may be thick with young talent in their defensive secondary, but the 23-year-old is very aware of the vacancy at the top.

"If I work hard -- I have to put up a fight -- I could play this year," Underwood said. "I think I have all the tools to play right away, I just have to be willing to work hard and give it 100 percent and learn the scheme."