Life without Kevin Durant began anew for the Nets on Thursday night. 

Their first challenge in Durant’s absence because of a sprained MCL? The team with the best record in the NBA, and the one standing between the Nets and the top of the Eastern Conference. 

Despite a strong start and a two-point game entering the third quarter, the Nets ran out of gas in the fourth and fell to the Celtics 109-98 at Barclays Center. 

The loss was only the Nets’ third in their past 21 games, but one they hope is not a harbinger after going 5-16 last season when Durant missed six weeks with an MCL sprain. This time around, they were on their way to a better start without Durant and led by as many as nine points in the first half before the Celtics’ defense suffocated them in the fourth quarter, holding them to 16 points. 

“They won the race to get the fourth quarter started aggressive,” Kyrie Irving said. “A few times, calls could have gone either way when the results ended up the way they are, and I feel like we definitely could have taken some better shots in the fourth quarter, got some defensive stops, but it didn’t happen for us tonight. And when you give up any opportunities for them to capitalize, they’re a great team, they’re gonna do so.” 

The Celtics (31-12) were also short-handed, playing without Jaylen Brown and Al Horford on the second half of a back-to-back, but they finished stronger to knock off the Nets (27-14). Jayson Tatum led the way with 20 points and 11 rebounds while Marcus Smart chipped in 16 points, 10 assists and six rebounds. 

Irving led the Nets with 24 points while Joe Harris, starting for Durant, had a season-high 18 points and T.J. Warren added 20 points off the bench. Ben Simmons had a season-high 13 assists and nine rebounds but went 0-for-3 from the field and did not score. 

“I love that we had 34 [3-pointers] up, [but] I don’t like that we were 12-for-32 from midrange,” coach Jacque Vaughn said. “That’s just inefficient. With Kevin, taking 32 midrange [shots], we can roll with that. But the other guys, that’s not the basket that we want to fit in. We take 10 more 3s or 15 more 3s, I love it. But those shots are inefficient. You end up being 12 of 32, that’s why you have 16 points in the fourth.” 

The Celtics took an 84-82 lead into the fourth quarter and promptly turned it into their biggest advantage of the night by opening the quarter on an 8-2 run with their second unit. 

Tatum and Smart then came back in the game and pushed it to a 12-2 run that extended the Celtics’ lead to 96-84. The Nets never got the deficit smaller than seven points the rest of the way. 

The Nets got out to a quick start on the night, leading for most of the first quarter and then trying to pull away with a 6-0 run in the second that put them up 42-33. But the Celtics soon one-upped them with an 8-0 run, again from their second unit, to get back in the game. 

Some strong facilitating from Simmons on the fast break — where the Nets held a 24-10 advantage — pushed the Nets’ lead again before the Celtics closed out the second quarter on a 15-5 run to take a 60-57 lead into the break, a sign of things to come in the second half. 

“You want to play the best team,” Simmons said. “The way they play, they’re very together defensively and offensively. They have some great individuals, but when you put it together, they play team basketball. They know their roles, they share the ball, they’re very consistent.”