Celtics point guard Rajon Rondo poses for the camera Monday in Waltham.	AP PHOTOSun staff photos can be ordered by visiting our MyCapture site.
Celtics point guard Rajon Rondo poses for the camera Monday in Waltham. AP PHOTO

Sun staff photos can be ordered by visiting our MyCapture site.

WALTHAM -- Regardless of how it may have appeared for nearly the past three months, Gerald Wallace says he's happy to be a member of the Boston Celtics.

The 31-year-old forward was acquired by the Celtics in the summer blockbuster trade that sent Paul Pierce, Kevin Garnett and Jason Terry to the Brooklyn Nets. Wallace was part of a return haul that included forward Kris Humphries, and guards MarShon Brooks and Keith Bogans. But the 6-foot-7 Wallace was not present when the group was introduced at a July press conference.

It seemed odd back then, and grew increasingly head-scratching as day after day passed without Wallace appearing in Boston.

Finally, the veteran one-time all-star answered questions at the Celtics' annual media day Monday at their training facility.

"I've been at home with my family, spending time with my family, enjoying it," said Wallace, who enters his 13th season. "Getting traded is a process that nobody likes to go through. It caught me off guard and shocked me. I was in the middle of (running) my camp, so I had an obligation to those kids so I wasn't able to come to the press conference. I just felt like I'd take the opportunity to spend more time with my family.

"I'm very happy to be here, especially with these guys that are looking for a new start. I think the main thing that a lot of people have taken out of this is that I didn't want to come, I didn't want to be here, I didn't want to be a part of it. That's so far from the truth. I've been traded three times in the past three or four years. This trade kinda caught me off guard, I didn't see it coming. I didn't know anything about it."

The young, rebuilding Celtics will begin training camp in Newport, R.I., on Tuesday with many questions. When will star point guard Rajon Rondo return from his ACL injury? Will first-year 36-year-old head coach Brad Stevens be overwhelmed? Opening Night is Oct. 30 at Toronto.

At least now, the C's know Wallace is on board.

Wallace said he found out about the trade June 27. He was spending time with family and friends at his house, playing cards and waiting for the NBA Draft to come on TV. Then he saw the details of the trade on his television screen. In his words he was "caught off guard and put into shock." He said he was never clued in by his agent that a trade to Boston was even a possibility.

"You kind of sit back and look at yourself and wonder what happened," said Wallace. "I'm happy to be here. I've always loved the city of Boston. Besides, I'm a Red Sox and Patriots fan, so I'm closer to my teams."

Wallace, an Alabama native and University of Alabama product, will make $10.1 million this season and is signed through the 2015-16 campaign. He's injury-prone -- he's played more than 75 games in a regular season just once.

He's also coming off his worst statistical season since 2003-04, averaging just 7.7 points and 4.6 rebounds in 30.1 minutes for a playoff Nets squad last year.

But Wallace is the only Celtic not named Rondo to play in an All-Star Game. He is a proven two-way threat.

Using his elite athleticism and versatility, Wallace relishes the opportunity to defend the opposition's best offensive player.

He also has career averages of 12.9 points, 6.2 rebounds and 1.5 steals.

"Gerald is a leader, he's a veteran," said Humphries. "He's a guy that, if we get up and down the court and play the style that we're talking about playing, he could be very effective. I think we can expect a lot from him this year."

Wallace's leadership skills will be tested. After the 33-year-old Bogans, he is the oldest player on the Boston roster.

He went from playing on an Eastern Conference contender to playing for a Celtics team that many expect to finish in the lottery.

Gone are future Hall of Famers Pierce and Garnett, and championship-winning head coach Doc Rivers, who bolted for a better situation in Los Angeles with the Clippers.

In are seven new players, who all very well could be key contributors.

There is no timetable for Rondo's return from last January's ACL injury. As Rondo put it, maybe winter, maybe fall.

"I think it's going to be a lot of fun with great energy," said president of basketball operations Danny Ainge. "I honestly don't know who the starting five will be, or who the second five will be."

Training camp should be interesting.

Follow Matt Langone on Twitter and Tout @MattLangone