SANTA CLARA, Calif. (Map, News) - The San Francisco 49ers spent draft day in the trenches, replenishing their depth on the lines that too often got dominated last season.

San Francisco picked defensive tackle Kentwan Balmer of North Carolina on Saturday with the 29th overall pick, claiming a stout run-stopper with enough athletic ability to play at end or nose tackle in the 49ers' 3-4 defensive scheme.

The Niners then pulled a minor surprise by choosing offensive guard Chilo Rachal of USC with their second-round pick, the 39th overall. Rachal is a physical talent with ample potential, but he expected to fall further down the board after leaving the Trojans one year early because of his mother's ill health.

"Both will be impact players on our roster, I'm confident of that," coach Mike Nolan said. "How extensive, we'll let that happen on the field. We'll play that out. ... I think they were the two best players at the time we chose."

Balmer developed into a likely first-round selection during his senior year with the Tar Heels, when the program was taken over by former Cleveland Browns coach Butch Davis. With extensive tutoring from an NFL-savvy staff, Balmer realized his enormous potential with an outstanding season in which ACC opponents double-teamed him on nearly every snap.

"We think very highly of him here, and besides being a good football player, he's got great character and leadership," Davis said. "You love his charisma, and really he spilled his guts on game day and played as hard as he could to turn this program around. ... I think he really, truly started to learn this year what it took to be a great player, that it wasn't good enough just to have that innate athletic ability, that it took a great deal of preparation."

Balmer's party with about 75 family members at North Carolina's football training complex exploded with excitement when Balmer was chosen. His father, Charles, has been a Niners fan since their glory days in the 1980s.

"There's a lot of tradition that the 49ers have, and there's a lot of great players," Balmer said in a telephone interview. "We were watching them, seeing that red and that gold, and we just loved it. It's in me."

Balmer could play a big role immediately with the departure of two-thirds of last season's starting defensive line. Marques Douglas signed with the Buccaneers last month after three seasons with the 49ers, while Young intends to retire after a 14-year career spent entirely with San Francisco.

Balmer knows linebacker Manny Lawson, who attended rival North Carolina State, and he can't wait to meet Young - even if the four-time Pro Bowler has retired.

"I'm going to be in his ear every chance I get," Balmer said. "He's going to have to push me away from him, because I'm going to try and get all the knowledge I can from him."

Rachal was excited to stay on the West Coast with the club that employed his idol, 11-time Pro Bowl guard Larry Allen, for the past two seasons. Though Allen, also a former second-round pick, seems headed for retirement, Rachal plans to model himself after the destructive blocker from Compton, which is also Rachal's hometown.

Rachal claimed he entered the draft - apparently without even consulting USC coach Pete Carroll - because his mother, Veronica Pickett, has a tumor in her stomach.

"I'm very happy my mom and dad will be able to do a five-hour drive down to see me play," said Rachal, whose two older half-brothers died due to street violence in South Central Los Angeles. "I was the one in the family that always made the right decisions."