Soon after Wyc Grousbeck’s group bought the Boston Celtics, Red Auerbach gave him some advice.

The team’s legendary president at the time “told me personally right when I came in, ‘you need instigators, not retaliators,”’ Grousbeck said.

Twelve years later, the rebuilding Celtics drafted what Grousbeck called an “instigator” when they took guard Marcus Smart of Oklahoma State with the sixth pick Thursday night.

The 6-foot-3, 227-pound Smart said he was “ecstatic” to join a team that had shown great interest heading into the draft.

With their other firstround selection, the Celtics addressed a critical need by going for a perimeter scorer, drafting 6-foot-6 swingman James Young from Kentucky with the 17th pick.

That’s two young, promising players for a team that has eight first-round picks in the next four years as it looks ahead to its second season since a blockbuster trade sent Paul Pierce and Kevin Garnett to the Brooklyn

Nets in July.

Smart and Young join forwards Jared Sullinger and Kelly Olynyk, first-round picks the past two years, in a promising young core.

The Celtics are continuing to rebuild after going 25-57, the third-worst record in club history, in their first season under coach Brad Stevens.

Smart averaged 18 points, 5.9 rebounds and 4.8 assists as a sophomore last season. He can play both guard positions and could team up with point guard Rajon Rondo or make Rondo expendable in a trade. Rondo’s contract expires after the upcoming season.

Drafting Smart doesn’t have “any effect on Rajon at all,” Grousbeck said. “When you’re rebuilding a team, you take the best available athlete and then you let it all work out. We’ve got an allstar point guard, so that’s not the question here.”

Smart is looking forward to playing with the eightyear veteran.

“Rondo was actually one of the guards that I liked watching,” Smart said. “He reminds me of me. He’s very versatile. He can affect the game in many ways.”

Smart plays with a competitiveness and physical nature that NBA coaches covet. He’s a solid defender but needs work on his offensive game.

“This kid is energetic. He’s a bull,” Grousbeck said. “He is a force and when I met him he filled the doorway. He’s just got that physique and that drive and that attitude that we really like around the Celtics.”

As a freshman last season, the 18-year-old Young was second on Kentucky with 14.3 points per game. He hit 40.7 percent of his shots and 34.9 percent from 3-point range. He led Kentucky with 20 points and seven rebounds in the team’s loss to Connecticut in the NCAA championship game