WALTHAM — It’s a calculated gamble but one Celtics  team President Danny Ainge knew he had to take.
When the Celtics got the news that Jeff Green  would need season-ending surgery to repair an aortic aneurysm – surgery that was successfully performed on Monday at the Cleveland Clinic – Ainge was down a key man on his bench.
The veteran forward – who turns 30 on Feb. 7 – guaranteed that he’ll make his Boston debut this Wednesday when the Celtics host the defending champion Mavericks at TD Garden. Pietrus, who has averaged 8.1 points and 3.1 rebounds a game in his eight NBA seasons, missed the first two weeks with the team after rehabbing from arthroscopic right knee surgery.
What can he give the Celtics?
“Obviously, I haven’t played for eight months so I’m going to be Mickael Pietrus from the first game,” Pietrus said. “But, defensively, you can always help your team do the littlest of things to make them be a great team. So if I can get in the game Wednesday, even five minutes or 10 minutes, whatever, I’m willing to help my team.”
Pietrus is one of the most genuinely enthusiastic and likable players in the NBA. Combine that will his defensive skills, and he can bring a lot of intangibles to the Green.
“That’s why I was excited,” Pietrus said with a wide smile. “That’s why I wanted to be a Celtic because I think – on the floor – me and KG and all the guys can bring the toughness that Boston had when we played them. They were so tough. It was hard for us to get a shot so I’m trying to get the same mindset. Get in the game, play hard and make sure we work hard, and at the end of the day, make sure we get the ‘W’.
“It was a good two weeks. I got to see downtown Boston a little bit, read the newspaper so obviously, there’s no snow yet so good thing – summertime in Boston. I’ve been watching my teammates and watching a lot of film so on Wednesday, I’ll be ready… Wednesday is going to be a great day for me!”
Pietrus tested his knee in practice last Thursday then worked with the second unit on Sunday before going full bore on Monday, not coming out to rest at all.
“Today I went through my first practice,” said Pietrus. “It feels good to be a Celtic. I had fun so hopefully, I’ll be back on the court Wednesday.”
Asked how close he was to 100 percent after knee surgery, Pietrus pointed to the watch of a reporter.
“You have a watch? Probably 48 hours,” Pietrus said. “I think I’ll be able to help my team. I went through practice with no pain. I told you guys I’d be ready to go in two weeks and two weeks came. I’m very happy I could go through practice with my teammates and get stuff done.”
Pietrus, who battled against the Celtics in the playoffs in 2009 and 2010 with the Orlando Magic , said he’s happy to be wearing the green.
“It feels good,” he said. “Look around, there’s 17 banners so I’m in a great spot. I just want to work hard and be available for my team on Wednesday.”