CHICAGO — The Boston Celtics got hit with a devastating emotional blow just as the playoffs were about to start. They dropped the first two games at home, too.

Just as things really were starting to look bleak, they began to show just why they earned the No. 1 seed in the Eastern Conference.

The Celtics rallied to knock off the Chicago Bulls in six games, and now they’re ready for a collision with John Wall and the Washington Wizards in the East semifinals.

“Sometimes, we lose sight of the important things in life,” Al Horford said after Boston knocked out Chicago 105-83 on Friday night. “You appreciate life at the same time when you don’t take for granted any of the moments. It was a rough couple of days for us to start the playoffs. The team wasn’t ready.”

Isaiah Thomas and his family were rocked by the death of his sister Chyna in a car accident the day before the playoff opener. The Celtics star attended funeral services in Washington on Saturday and was expected to be available for Game 1, but Coach Brad Stevens said that was not the most important issue.

“(Saturday) is a lot more important than Sunday,” Stevens said. “It’s difficult, but it’s a basketball game. He’ll be ready to play. And if he decides when he gets there it’s too much, that’s OK. That’s fine.

“This (being with his family) is a lot more important.”

Against the Bulls, Thomas played through tears at times. But he also got the support he needed from his teammates and gave the Celtics a big lift in the series.

“He’s gonna have a busy 24 hours,” Jae Crowder said. “He’s shown he can overcome a lot. We’re his family, he’s going to be with his family, so I think he’ll be able to bounce back. But we know he’s going through a lot, and he wants us to prepare, and that’s what we’re gonna do. We’re gonna prepare, and when he gets back he said he’ll be ready to go.”

Avery Bradley did what the Celtics needed him to do against Chicago, whether he was sticking with Jimmy Butler or pouring in the points. He scored a career playoff-high 24 in Game 5 and almost matched that with 23 in the clincher.

The Celtics also benefited from a lineup switch after Game 2, going with Gerald Green over Amir Johnson. All he did was score 18 points in Game 4 and 16 in Game 6 to help Boston win a tougher-than-expected series.

“The lineup change I thought really helped us,” Horford said. “Bringing Gerald Green in and moving me to the 5, I felt like we really were able to spread them out and take advantage of certain looks we haven’t gone to all year. I think that for us, that was the difference. Once we made that adjustment, we were harder to guard. We got it together, and we got it going.”

How far can they go?

The Celtics advanced in the playoffs for the first time since 2012. They looked more like the team that led the East with 53 wins to finish two games ahead of defending champion Cleveland and Toronto as this series wore on.

Sure, it didn’t hurt that the Bulls’ Rajon Rondo sat out the final four games because of a broken right thumb. Chicago struggled in a big way without him, but Boston had something to do with that, too. And in Game 6, it was no contest.

The Celtics set the tone by hitting 3s on their first three possessions on the way to a 13-point halftime lead.

They buried Chicago in the third, outscoring the Bulls 34-18. Things got so lopsided that Thomas gathered his teammates near the baseline late in the quarter and screamed: “That’s a wrap for these (expletives)!”

It was a big exclamation mark for a team that looked as if it might be on the way to a quick exit after Game 2. They’re staring at another big challenge, trying to slow Wall and the Wizards.

But Crowder likes what he’s seeing from the Celtics.

“A lot of underdogs in this locker room,” he said. “A lot of guys who had to prove themselves in this league … who’ve been through the ropes, who’ve had to prove themselves. It’s in our DNA.”

The Wizards battled with Atlanta in the opening round with the home team winning the first five games of series until Friday when John Wall set a career playoff-high with 42 points and the Wizards finally broke through on the road to end Atlanta’s season. It was a much-needed confidence boost heading into a series lacking the home-court advantage.

“We can win on the road,” said Bradley Beal, who also came up big in the series-clinching victory with 31 points.

Wall and Beal will certainly lead the way against the Celtics. Atlanta Coach Mike Budenholzer said they are a challenging 1-2 punch for any team to defend.

“When you have multiple pick-and-roll players, multiple ball-handlers, that can move you side to side,” he said. “And they’re different, too, so how you want to guard one isn’t how you want to guard the other. … No doubt they’ve both improved and both are playing well. Those guys are a handful.”

Wall averaged 29.5 points in the six games against the Hawks. Despite struggling early on with his shot, Beal finished the series at 25.8.

“That’s how they have to play for us,” center Marcin Gortat said. “They’re both the head of the snake. They both have to be productive for us.”

They might need a bit more help deeper into the playoffs. One option is Markieff Morris, who battled foul trouble through much of the series against the Hawks before settling down in Game 6. He was called for only two fouls, finishing with 17 points and eight rebounds.

But as long as the Wizards have Wall and Beal, they’ve got a chance.

“Listen, they’re bad boys, both of them,” Gortat said.

“When they’re locked in, and when they’re playing team basketball, they’re ridiculously good. That’s enough.”