Boston draft picks Semih Erden of Turkey (86), J.R. Giddens of New Mexico (4) and Bill Walker of Kansas State (12) pose at the team’s training facility in Waltham, Mass., yesterday.

AP / Charles Krupa

WALTHAM, Mass. — The last three players to pose for pictures at a news conference while holding Celtics jerseys in front of them were Kevin Garnett, Ray Allen and Paul Pierce.

Eleven months after Boston announced the trade for Garnett, the Celtics won the NBA championship.

Yesterday, three other players assumed the pose — draft picks J.R. Giddens, Bill Walker and Semih Erden.

Good luck trying to get playing time, guys.

It’s not that three newcomers, introduced at a news conference the day before the team’s rookie-free agent camp, lack talent.

But cracking the rotation on the NBA’s best team will be difficult. It would become tougher if the Celtics strengthen their roster with free agents.

“There’s a lot of good players out there,” Celtics general manager Danny Ainge said. “With our team right now, we have a lot of people that want to come play for the Boston Celtics. So that’s a good thing. These (draftees) really haven’t proven anything or done anything yet, other than have a lot of potential.

“The world is full of unfulfilled potential.”

Ainge doesn’t even know if any of them will be at the team’s regular training camp. He said having Giddens or Walker play overseas next season is a consideration.

Giddens, an athletic 6-foot-5 guard from New Mexico, has the best shot at making the Celtics after being taken with the 30th and final pick of the first round. Walker, a 6-6 forward from Kansas State, will be sidelined for about three weeks and will miss the rookie camp because he’s scheduled to have minor surgery on his right knee today.

Erden, a 6-11 center, has one year left on his contract with his team in Turkey and intends to go to the NBA the following season.

Giddens played two seasons at Kansas and two more after transferring to New Mexico, where he became the team’s best player. He knows he’ll have a much smaller role with the Celtics.

“At Kansas, I wasn’t the main guy on the team and I had to play my role,” he said. “So I don’t feel like it’ll be any different. I’m a young guy. I’ve got a lot to learn. Guys know so much more than me, so playing a lesser role than KG, Paul Pierce, Ray Allen, those guys, it’s not that hard.”

Especially with what Giddens has been through.

In May 2005, he was stabbed in a bar fight after his second season with Kansas, and pleaded no contest to a misdemeanor battery charge. At New Mexico he was suspended twice in his first season but feels he matured last season under new coach Steve Alford.

“The journey’s just begun now,” Giddens said. “I’ve turned over a new leaf and it’s time to try to prove myself at the next level.”

Walker also had his share of setbacks — major surgeries on his right knee as a high school freshman and on his left knee as a college freshman, his only season at Kansas State. He suffered his latest injury during a pre-draft workout with Golden State.