Markieff Morris grabs his leg after rolling his ankle after making a shot against Al Horford in the second quarter. Morris’s shot broke a 42-all tie, but the Celtics rolled to a Game 1 victory from there. (Maddie Meyer/Getty Images)

Markieff Morris tried to show icy resolve and silent strength.

The pain was shooting from his left ankle, a feeling so intense and unfamiliar that he initially thought the bone had snapped. Morris had to leave Game 1 of the Eastern Conference semifinals, but he deliberately walked to the sideline without wincing. However, by the time his slow steps had finally removed him from the spotlight of the court, Morris began to limp. Soon, the Washington Wizards also would pull up lame, with an uneven performance against the Boston Celtics resulting in a 123-111 loss Sunday.

“Don’t know nothing as of yet,” Coach Scott Brooks said about the extent of Morris’s injury. “I watched the video. It didn’t look good.”

When asked whether he would play in Game 2 on Tuesday night, Morris emphatically told reporters: “For sure. Hell, yeah.” That contradicted the visible evidence: Morris’s foot was so swollen that he was unable to put on his left shoe.

The Wizards only can hope Morris’s declaration proves to be more than just machismo because without the full-strength powers of the starting unit the Wizards will be at a significant deficit.

Isaiah Thomas scored a game-high 33 points against guard Bojan Bogdanovic and the rest of the Wizards. (Jonathan Newton/The Washington Post)

On Sunday, Washington’s starting five produced a plus-13 while together during the team’s rousing first quarter. The Wizards scored 38 points, shot 61.5 percent from the field, drilled four three-pointers and dominated the glass for a 14-5 advantage. But the five never formed a unit again, and all other lineups finished minus-25 for the rest of the game.

Bradley Beal led the Wizards with 27 points and John Wall finished with 20 points and 16 assists — and eight turnovers — but Washington wandered defensively and allowed a season-high 19 three-pointers.

“They were a little more aggressive than we were,” Beal said, referring to the Celtics’ overpowering third quarter, in which they outscored Washington 36-16.

“Our defense slipped a little. We lacked some IQ and focus.”

Early in the game, the Wizards looked unstoppable in jumping to a 22-5 lead. They shot with deftness from the perimeter but also bullied Boston’s starting lineup. Marcin Gortat loved his role as the lone true center on the floor, and his 4-for-6 shooting forced Celtics Coach Brad Stevens to yank swingman Gerald Green and send in defensive-minded brutes.

“I thought we were in trouble,” Stevens admitted.

John Wall had 20 points and 16 assists against guard Marcus Smart and the Celtics, but it wasn’t enough in a Game 1 loss at TD Garden. (Winslow Townson/USA Today Sports)

In the first quarter, Washington silenced the TD Garden. But at the 7:18 mark of the second quarter, a stark stillness filled the Wizards’ sideline.

Morris had the left side of the court cleared out for a one-on-one against Boston’s Al Horford. Morris didn’t dig in and drive. Instead, he liked his chances from 16 feet away, stepping back into the midrange shot that he has dined on all season. Horford attempted to defend the jumper and ventured in too close, leaving no room for Morris to safely land.

The slow-motion replays were not suitable for the squeamish. Morris landed on Horford’s left foot, causing his own left ankle to bend unnaturally toward the court. The shot swished, but Morris crumpled, struggling in pain. Morris may have experienced previous foot and ankle issues, but the somber expressions of his teammates revealed this one was far more troubling.

“He was in a lot of pain. We were just hoping it wasn’t his knee,” Wall said. “He has an issue kind of spraining his ankles all the time, but we told him if you don’t shoot the free throw, you can’t come back in, and we was just trying to get his space and take as much time as he needed.”

Morris finally climbed to his feet. He chewed on his mouthpiece and slightly acknowledged Horford’s pat on his shoulder before gingerly walking to the foul line.

After Morris’s free throw pulled the Wizards ahead 45-42, the team committed a foul to get him off the floor. Morris moved like a man three times his age, his slow steps leading to the scorer’s table, then to the Wizards’ bench and, finally, to the tunnel. Although Morris didn’t want to reveal his pain to the 18,624 fans, by the time he reached the hallway with team athletic trainer Corey Bennett, his laborious gait had turned into an uncomfortable hop.

“This was my worst one. I kind of tend to twist my ankles,” Morris said. “That’s my injury. Ankle twisters. This was by far the worst one.

“I honestly thought it was broke,” Morris continued. “They got the swelling to go down a whole lot, and it almost was like the size of a softball.”

For long-suffering Wizards fans, the sight of a hobbled Morris had to conjure bad memories of the last time this team was in the second round.

In Game 1 of the 2015 conference semifinals against the Atlanta Hawks, Wall injured his left hand and wrist. Had it not been for those five small fractures, the Wizards believe they would have won that round and advanced to the Eastern Conference finals.

The question now: Will one severely sprained ankle sink the Wizards again?

After Morris left the game, the Wizards lost their interior size-and-strength advantage. Gortat remained, but without a menacing Morris to share the load, he no longer dominated. Before the Morris injury, the Celtics grabbed only two offensive rebounds. After he left — the Wizards responded by playing small-ball lineups with Otto Porter Jr. to the four spot — Boston pulled down 10 more.

“He’s a matchup problem,” Brooks said about Morris. “He can score inside. He can score outside. He puts the ball on the floor. He gets six, seven, eight rebounds a game, but he blocks out. He knows how to play. He’s a smart basketball player. We definitely missed him, but I will tell the guys — there’s no excuse. We got beat.”