Can Harden turn back the clock once again?

The 76ers lingered on the TD Garden parquet after the final buzzer sounded Monday night, dapping up one another to celebrate their Game 1 upset over the Celtics. Their joyful reactions looked far from ostentatious, but James Harden had seen enough.

“It’s one game, bro,” said Harden, as he motioned his teammates to retreat to the visiting locker room. “It’s one game.”

The Sixers should be thrilled. Without superstar center Joel Embiid, they managed to steal the opening contest of their bestof-seven second-round series against the top remaining seed in the Eastern Conference. But Harden, who scored a gamehigh 45 points, wanted his teammates to understand that plenty of work is still ahead.

“I told the guys, ‘Don’t get too happy about it,’ ” Harden said following Philadelphia’s 119-115 victory. “We’re coming in here to get Game 2 as well. That’s the mind-set we have to have as a unit. Whether Jo comes back or not, we’ll be ready to go.”

In the days leading up to Monday’s tipoff, the biggest questions about the Sixers revolved around Embiid, who suffered a sprained LCL in his right knee in Game 3 of their firstround series against Brooklyn. Would he play? Would anyone else step up in his absence?

After Game 1, the first question remains the same. Embiid, listed as doubtful, did not play, instead watching in street clothes from the end of the bench. His timetable for a return remains uncertain 12 days after the injury.

The second question, however, has shifted. With Harden leading the way, multiple Sixers not named Embiid delivered.

But can they do it again?

Harden’s stat line stands out as a blast from the past. He made 17 of 30 shots, the most attempts he has logged in more than two years. His 45 points matched his playoff career high, first set in Game 4 of the 2015 Western Conference finals.

“I haven’t felt one of those zones in a minute,” Harden said. “It felt really good. Just to be aggressive and shoot the basketball and do what I want, that felt very good. I’m capable of doing it. It felt good to make shots, to give ourselves a chance.”

With Embiid sidelined, the 33-year-old Harden took it upon himself to be more aggressive. When the Celtics made 17 of their first 20 shots, Harden helped the Sixers keep pace with 16 first-quarter points. He scored at ease — both at the rim and from behind the arc — presenting matchup problems for the Celtics throughout the game.

Embiid’s absence turned Harden into more of a scorer than a facilitator. The reason Monday’s stat line seemed so rare for him, Harden said, is that the Sixers don’t need him to attack at that frequency.

“It’s not that I’m not capable of doing it,” he said. “It’s just, this is my role for this team. Now if you want me to do this? Then I can do that as well. I don’t think a lot of players can do that.”

Harden surely is not lacking confidence. And apparently neither are the rest of the Sixers.

“We really believe,” said coach Doc Rivers. “James has missed games, we win. Joel has missed games, we win. That’s the difference between this year’s team and last year’s team. We have a bunch of those street fighters. They believe.”

The Sixers received major contributions across the board Monday.

Backup center Paul Reed, starting in place of Embiid, made four clutch free throws in the final minute. Guard De’Anthony Melton came off the bench to knock down all five of his 3point attempts in the first half. Guard Tyrese Maxey broke out of his slump against the Celtics to score 26 points, including a critical running dunk after Malcolm Brogdon passed the ball right to him with 30 seconds to go.

The Sixers have prided themselves this year on their resilience. According to Rivers, the team’s mind-set all week was rooted in their fight and belief.

“If we can get to the fourth quarter, we’re going to win the game,” he said. “That’s how we felt. That doesn’t mean it always happens, but that’s how we felt.”

Now, with Game 2 set for Wednesday, Harden and the Sixers have another opportunity to prove their mettle on the road.

They’ll head into tipoff with certain adjustments, such as getting more shots up and trying harder on defense, but there’s one key Harden certainly does not want to change: “Being ultra-confident.”

“That’s all it is in the playoffs,” Harden said. “If you have confidence, you can run through and beat anybody. We’ve seen it so far this year.”