This time last summer, Matt Barnes was coming off an electric postseason with Golden State — capped by the No. 8 seed’s stunning upset of the 67-win Dallas Mavericks — while his mother, Ann, was gearing up for another emotional wave as one of the team’s biggest cheerleaders from the family home in nearby Sacramento, Calif.

Neither had a clue what the next year would bring.

After re-signing with the Warriors for one year and $3 million when hopes for more riches and security failed to materialize, Barnes’ life quickly turned upside down.

On Nov. 1, as the Warriors were set to tip off the season, Ann was diagnosed with Stage IV cancer. There was nothing that could be done and 26 days later, she passed away with her son by her side.

“My mom was my best friend,” said Barnes, who now finds himself in Phoenix as the newest Sun after officially signing a one-year contract for the veteran’s minimum Tuesday. “You only get one mom. She was gone so quickly … it was really a roller coaster. The season had started, it was time to play, but I just never really got my head back.”

Suddenly the Barnes that endeared himself to Warriors fans for his incredible energy and athletic feats had been replaced by a more withdrawn and troubled player. Named one of three captains by coach Don Nelson before the season, Barnes’ playing time dwindled while frustrations (three flagrant fouls, two of them level two fouls) mounted.

The Warriors were a tightknit team. Barnes has the slogan for the 2007 playoff run “Believe” on his neck amid his many tattoos. When Ann passed away, the entire team — and some of their moms — came to the funeral in a show of support. She was buried in her own custom- ized Warriors jersey.

“Even when she was hurting, she would always tell me to play because the team needed me,” he said. “I wanted to play for her, but I just never really got my head back. I was kind of under the weather the whole season.”

But the sun is beginning to shine again. He sought out counseling in the spring and got a handle on his emotion. His fiancée, Gloria, is expecting twin boys in December. And he has gone from a team that began each season with hopes of making the playoffs to a team with much loftier goals — and one which can really make use of his talents.

“(Through counseling) I got my feelings out and talked about it and I’m at peace with where she’s at and that she’s watching,” he said. “Now I feel I’m ready to go back out there and duplicate and even go further than what I did a couple of years ago.”

The Suns could wind up being the huge beneficiary.

A former high school all-American wide receiver in Sacramento, Barnes has some of the physical tools of a Shawn Marion — he guarded everyone from point guards to centers at Golden State, has great leaping ability and loves to finish on the break. But also brings the no-holdsbarred mentality of a Raja Bell — doing the dirty work defensively.

“My whole career has been a one-year deal,” he said. “That’s why I’ve always been hungry. There is no relaxing.”

The knock against Barnes has been that his effectiveness lies in playing amid chaos, and that he struggles in a slower, more structured game. But while the Suns figure to be more deliberate with Shaquille O’Neal in the middle, the Suns still want to use their signature up-tempo, createmismatches style that was effective for him in Golden State.

Barnes could start or back up Grant Hill at small forward. He can defend point guards with his quickness and big forwards — as he proved with Dirk Nowitzki in the playoffs — with his toughness. He shot 36 percent from 3-point range two years ago, although that part of his game (29 percent) also tumbled last year.

The Los Angeles Clippers and Lakers and Boston all looked at Barnes, but no one bit. When Barnes heard the Suns were interested he told his agent to make it happen, although he will make less than a third of what he made last year.

“It’s a home run for us,” Suns general manager Steve Kerr said. “We didn’t think we could get him. But for players, the free-agent market was really tough and there wasn’t a lot of money out there. We wanted to find another wing, another shooter, and we didn’t think we’d do this well.”

BONUS SHOTS: Kerr said because Barnes can play so many positions, the Suns now have the luxury of using their 13th and final roster spot on any type of player instead of a backup post player as assumed. If Goran Dragic winds up in Phoenix this season, that spot will almost certainly be used on a veteran with point guard experience. … Sid Craig, co-founder of Jenny Craig Inc., and a minority owner of the Suns along with his wife, died Tuesday at the age of 76. He is survived by his wife, five children and 13 grandchildren.