Despite entering the 2017 NBA playoffs as the No. 1 seed in the Eastern Conference, several members of the Boston Celtics reportedly felt disrespected by national observers who persisted in picking the second-seeded Cleveland Cavaliers over the Celtics to go to the NBA Finals. (Cough.) Boston’s bid to prove the doubters wrong got off to a rough start on Sunday, with the No. 8 seed Chicago Bulls coming into TD Garden and stunning the C’s.

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The Bulls battered Boston on the boards in the first half and Jimmy Butler took over in the second, leading Chicago to a 106-102 win that wrested away home-court advantage from the East’s top seed. The upset continued a harrowing opening weekend of the postseason for teams at the top of the Eastern bracket …

… and put the Celtics, who won 53 games this season but split their season series with Chicago 2-2, in a precarious predicament.

After a quiet start that saw him miss seven of his first nine shots, Butler came alive late in the third quarter, scoring eight points in the closing 1:28 of the frame to keep the score knotted at 74 heading into the final 12 minutes. He kept the pressure on in the fourth, scoring 15 just under nine minutes of floor time — a new playoff career-high for single-quarter scoring for the All-Star swingman — to help fuel a 16-6 run that turned an 88-87 Celtics lead with 5:33 remaining into a 103-94 Bulls advantage after a Butler layup wth 47 seconds to go.

Butler led the way, scoring 10 straight during one fourth-quarter stretch and 23 of his team-high 30 points after halftime. He also pulled down nine rebounds, dishing three assists, and notching one steal and one block — an emphatic rejection of a layup attempt by Celtics star Isaiah Thomas with Chicago up seven and just over 90 seconds left:

As monstrous as Butler was after intermission, though, he had help on Sunday. Dwyane Wade struggled with his shot — especially one particular shot — but he supplemented his 11 points on 12 shots with six assists, five rebounds, two steals and two blocks, including one big rejection of Boston center Al Horford at the rim that led to a five-point fourth-quarter swing:

Former Celtics hero Rajon Rondo likewise struggled with inefficiency, needing 15 shots to score 12 points, but he added seven rebounds, six dimes, two steals and a block with just one turnover in his 27 minutes. Butler’s biggest boost, though, came from the frontcourt, where big men Robin Lopez and Bobby Portis dominated Boston on the interior to help spark Chicago to a 53-36 rebounding edge, including 20 offensive rebounds.

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Lopez, who entered with 22 career postseason games under his belt from his days with the Phoenix Suns and Portland Trail Blazers, just kept busting Boston up inside, scoring 14 points on 6-for-10 shooting with 11 rebounds. Eight of those came on the offensive glass, including a huge board in traffic with 1:41 left that forced a foul and sent him to the line for two free throws that put Chicago up 99-92 late.

Portis, the 22-year-old reserve power forward out of Arkansas, took full advantage of inattentive Celtics defense to score 19 points on 8-for-10 shooting, including a 3-for-4 mark from 3-point range, to go with nine rebounds, three assists, two blocks and multiple clutch plays in a sterling 29-minute postseason debut:

Despite the Bulls’ late-fourth rally, the Celtics made it interesting in the closing moments. After Butler split a pair of free throws to give Chicago a 104-97 lead with 19 seconds remaining, Thomas — playing with a heavy heart after losing his 22-year-old sister, Chyna, in a car crash on Saturday — drilled a pull-up 3-pointer to get Boston within four at 104-100 with 14 seconds left.

On the ensuing inbounds pass, Bulls guard Jerian Grant tried to lob the ball to Butler, but Celtics defender Avery Bradley reached in to deflect the pass:

After replay review, the officials awarded Boston possession, and Thomas drove past Lopez and through Butler for a twisting layup that cut the deficit to two with 7.5 seconds left:

After a timeout, though, the Bulls tried again. This time they were able to get the ball to Butler, who took a foul from Crowder and knocked down a pair of freebies to push the lead back to four with 3 seconds left.

Those free throws put the game out of reach, and the Celtics in an 0-1 hole, despite a brilliant outing from Thomas. Playing through frankly unimaginable grief, the All-Star scored a game-high 33 points on 10-for-18 shooting (3-for-7 from 3-point land, 10-for-12 at the free-throw line) with six assists, five rebounds, one steal and just two turnovers in 38 minutes:

But Thomas’ heroics, a strong game from Horford (19 points, eight assists, seven rebounds in 40 minutes, though the final 17 1/2 of those featured zero rebounds) and 14 3-pointers weren’t enough to overcome the shotmaking of Butler and Portis, or Chicago’s ability to clean the glass:

The good news for the Celtics is that history’s still on their side here …

… but they’ll need to turn in a much better effort to get level, and to demand the respect they want.

They’ll get the chance to even things up when Game 2 tips off at 8 p.m. ET on Tuesday.

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Dan Devine is an editor for Ball Don’t Lie on Yahoo Sports. Have a tip? Email him at devine@yahoo-inc.com or follow him on Twitter!

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