Losers in the NBA playoffs often check off what-ifs as they head home for the summer.

For the Hawks, the list is as long as their perpetual injury report and as painful as the handful of plays that led to a first-round loss to the Celtics.

“Yeah, it hurts,” Hawks guard Joe Johnson said after Boston’s series-clinching victory Thursday. “The last three years we advanced and made it to the second round. After last year, we looked at it like we was ready to make that jump.

“Give [the Celtics] credit. They are a great veteran team that has been around the block, knows what it takes. They came into our house and stole one. That’s all they needed.”

Celtics coach Doc Rivers cited that Game 2 victory at Philips Arena as the turning point. Boston won without suspended point guard Rajon Rondo to take home-court advantage away from the Hawks, then closed them out at TD Garden on Thursday with an 83-80 victory.

The Hawks rallied with a 14-2 run in the fourth quarter of Game 6. They led 79-78 in the final minute before faltering.

“You’ve got to give Atlanta a lot of credit, you really do,” said Rivers, a former Hawks point guard. “Atlanta is criticized so much about who they are and all that stuff. And they had 10 times tonight where they could’ve went away and said, ‘You know what? We gave it great effort.’ And they just kept putting the pressure on us.”

The final game was, in many ways, a microcosm of the Hawks’ season.

The Hawks had a key player out with injury (Zaza Pachulia) and others hobbled by ailments (Josh Smith and Al Horford). Their intensity on defense gave them a chance against before lackluster offense did them in.

The Hawks head into the offseason believing things could have been different if they had been healthier. That doesn’t change the reality that they still could have defeated the Celtics with sharper execution.

“We overcame adversity throughout the season,” Smith said. “Obviously it’s disappointing that we couldn’t do something special this season. The road was paved as good as it’s ever going to get for us, but we didn’t take advantage of it. That’s the frustrating part.

“But we can’t hang our heads. We have to look at all the positives this team did this season. ... It’s not all negative.”

The Hawks posted a 40-26 record during the lockout-shortened season, fourth-best in the Eastern Conference. They were 7-4 when Horford, a two-time All-Star, went down with a torn pectoral muscle Jan. 11 that required surgery.

That was the biggest injury hit for the Hawks because Horford is their most efficient scorer in addition to an all-around producer on offense and defense. He returned to play against Boston in Game 4, but wasn’t at full strength.

“I’m proud of the guys the way they reacted and came out every night and competed,” Horford said. “I feel like each guy has had their moment this year. I just kind of came in at the end trying to help us out. Unfortunately for us, the run ended.”

Horford’s injury was the biggest blow for the Hawks. There were other key injuries that added up.

Guard Kirk Hinrich missed the first month after offseason shoulder surgery. When guard Willie Green returned from a 10-game absence, guard Jannero Pargo went out for 10 games after an appendectomy. Pachulia, who had filled in well for Horford, suffered a foot injury April 13 and never returned to the lineup.

Lots of playoff teams have dealt with significant injuries. That doesn’t mean the Hawks won’t wonder what might have been with better health.

“Man, I’ve been saying that from Day 1,” Hawks coach Larry Drew said. “If we would have had a full squad. If we would have had Zaza. All the games that Kirk missed. ... I’m proud of these guys for responding the way they did given all the injuries. Everyone counted us out.”