It wasn’t pretty. Not the NBA lockout. Not the 0-3 start. Not the losses of Jeff Green and Chris Wilcox to heart surgeries. Not the two five-game losing streaks. Not the way Paul Pierce started the season, Ray Allen ended it or everything in between that involved Jermaine O’Neal. But it’s over.

The 2011-12 Celtics regular season is in the books, resulting in another Atlantic Division title to toss into the supply closet along with the franchise’s 21 others that mean little compared to the 17 NBA championship banners hanging from the rafters. All in four months work for Kevin Garnett.

“We’re a very, very motivated group,” said Garnett. “Individually, we have a lot of pride. Together, we play hard as sh*t. Like I said, we’re a very prideful team. Like I always said, man, when you come in here and put that jersey on, there’s a lot of responsibility that comes with that, and we don’t take that lightly in here.”

The Celtics finished 39-27, capturing the fourth seed as the division winner, but finishing a game behind the Hawks (40-26), who will host Game 1 of their first-round playoff series on Sunday at 7 p.m. on TNT (full schedule here), presumably without injured centers Al Horford and Garnett’s personal favorite Zaza Pachulia.

“This Atlanta team is a very exciting team — athletic, a better team since we’ve seen them, a more mature team,” said KG. “Smooth, Josh Smith, has played to me some of his best basketball. Joe Johnson is classic Joe Johnson. And they’re coming together as a team. … They’re feeling good about themselves, and that’s a thing we have to reckon with. And we’re going to prepare for them starting tomorrow.”

The Celtics haven’t been without their share of injuries, either, even excluding the season-ending surgeries for Green, Wilcox and O’Neal. Allen has missed the last nine games with bone spurs in his ankle, Greg Stiemsma has two bad feet, and both Rajon Rondo (back) and Mickael Pietrus (knee) returned just in time to beat the Bucks in Thursday’s finale. Only Pierce (60), who left with a sprained big left toe before returning without the aid of a wheelchair, played more games this season than Garnett (59).

“When your guys are out there and you’re playing — when you step on the floor — it’s not to entertain,” said Garnett, who returned from a sore hip flexor of his own. “It’s to go hard. That’s exactly what we did.”

It’s what they did ever since entering the All-Star break on the heels of a dreadful loss to the Thunder in which the Celtics allowed 119 points and trailed by as much as 27 points. Since, the C’s own a 24-10 record — the third-best ledger in the league in that span behind each conference’s No. 1 seed (the East’s Bulls and West’s Spurs).

“We believe in ourselves,” said Garnett. “We believe in our system. We believe in our coach. We have a lot of confidence in each other. Our core is a group that is very confident, and it leashes out to the others. We did have a rough start. … I think once we hit our stride, once we got a rhythm, once we got back from the All-Star break, it was more about guys understanding the system. They had it down. New guys that were new to our system knew what to expect. We knew what to expect from them. And then we just played.”

It’s a good thing he trusts Doc Rivers, because even Garnett, one of the oldest of those guys, had to learn new tricks within that system. His move to center along with Avery Bradley‘s emergence as a legitimate NBA shooting guard transformed the Celtics from a borderline playoff team to a legitimate contender in the Eastern Conference.

“I hate the five spot,” said Garnett, once again. “I don’t keep track of how I’m playing. I go by how my body’s feeling. Obviously, I’m a confident person. You put me anywhere on the floor, I’m going to play it to the best of my ability. It’s not a preference of mine, but it’s something that my team needs, so I don’t think about it.”

Garnett even joked that he played point guard as a member of the Timberwolves in their 4-2 loss to the Lakers in the 2004 Western Conference semifinals. He averaged 23.7 points, 13.5 rebounds and 4.5 assists in that series. But those days are long gone. Garnett is in the final season of his five-year deal with the Celtics, and perhaps the last of his NBA 17 seasons, but not before at least one more shot at that 18th championship banner.

“We’ve been building,” he said. “Now we’re at the postseason, where everything happens. And I feel like we’re prepared. We’re ready.”