Boston, MA (AP)  -- The Boston Celtics picked guard J.R. Giddens of New Mexico with the 30th pick of the NBA draft Thursday night and coach Doc Rivers said his defensive skills give him a chance to contribute to the world champions next season.

The Celtics went into Thursday night's draft with the last pick in each of the two rounds after winning the title last week in a six-game series against the Los Angeles Lakers.

After taking Giddens, the Celtics obtained the draft rights to 6-fooot-6 forward Bill Walker of Kansas State for cash. Walker had been taken by the Washington Wizards with the 46th pick.

With the 60th and last pick of the draft, Boston chose 6-foot-11 center Semih Erden of Turkey. He averaged 6.5 points in four seasons in the Turkish League.

The 6-foot-5 Giddens was fourth in the Mountain West Conference with 16 points per game and first with nearly nine rebounds per game as a senior. Giddens spent his first two seasons with Kansas and his last two with New Mexico.

Celtics general manager Danny Ainge has said it would be difficult for the player the Celtics draft in the first round to contribute as a rookie. But Rivers didn't rule it out.

"We think he has a chance to fight for minutes right away because of his defense," Rivers said. "He's got incredible wingspan, great feet, and we feel that defensively he can be an NBA player right away. The other things we'll work on."

Giddens had behavioral problems at both schools.

He pleaded no contest to a misdemeanor battery charge after an incident at a Lawrence, Kan., bar in which he and others were stabbed. He was hospitalized with a slashed artery in his leg and received 30 stitches.

He was placed on probation for a year and ordered to take anger management classes, then left for New Mexico. He also was suspended at New Mexico for his attitude as part of the team.

"I feel like I've overcome those things," Giddens said. "I was just a young guy, immature, made some bad decisions. ... Now that I'm older, I feel I can do a lot better."

Rivers was well aware of that background.

"He's had some run-ins with people. Steve Alford, who coached him last year, thought he was terrific," Rivers said. "That's good enough for us."

Giddens worked out for the Celtics on Wednesday, and Rivers said he was very competitive.

"We knew three or four teams (picking) right in front of us liked him. Several guys dropped and fell to those teams," Rivers said. "We thought as of like the 24th pick (of) the two guys that we liked one of them would be there."

Giddens knows it will be tough to earn playing time on a championship team.

He plans to "try to earn a position and, if I'm, fortunate enough to get some playing time, I'll be happy, but if not I'll sit on the bench and clap."

In two seasons at Kansas State, the 6-foot-6, 220-pound Walker averaged 15.3 points per game. Last season. He had 196 rebounds and 17 blocks in 31 games.