Sabrina Ionescu came alive at exactly the right time for the Liberty.

Only ahead by one point early in the fourth quarter, she sprinted down the court in transition, putting the defender behind her to knock down a 3-pointer.

Ionescu continued her tear by staying aggressive, getting into the paint and knocking down foul shots. She also was able to find her teammates, dishing out four assists.

And she helped the Liberty to their largest lead of the game to that point — nine points — with a huge 3-pointer with less than four minutes to go.

The star guard made up for a scoreless first quarter and put together a 21-point night to rally the Liberty — who trailed by 13 points in the first half — to a 91-76 win over the Chicago Sky on Thursday night in front of 17,758 fans, the largest crowd ever for a Liberty game at Barclays Center.

“I was getting good looks at the basket, they were just long … so kind of just believing in the work I’ve put in,” said Ionescu, who scored 11 of her 21 points in the final quarter. “I shot a lot, and I know they’re going to go in if I continue to get to my spots. I kind of hung my head at halftime and then came back to start that third with kind of an understanding I need to go out there and get the ball in the basket for this team to win. Thankful that I had that opportunity to get out there and get good looks.”

Breanna Stewart tallied 19 points, and Jonquel Jones added 18 points and 13 rebounds in what was a tough night on the boards against Sky stars Angel Reese and Kamilla Cardoso.

With Liberty forward Betnijah Laney-Hamilton out with a right knee injury for the second consecutive game and considered day-to-day, Leonie Fiebich stepped up and finished with a WNBA career-high 13 points — including four 3-pointers.

The Liberty would trail by as many as 13 in the opening half as the Sky dominated the paint, scoring 56 points inside to the Liberty’s 28.

The Sky’s top scorer, Chennedy Carter, got to the basket for easy layups, finishing with 22 points.

Reese scored 10 points and had 10 rebounds for her WNBA record 15th consecutive double-double.

The Liberty gave up several “easy baskets” at the beginning of the game, head coach Sandy Brondello said.

“Coming off a back-to-back, I’m sure it’s no surprise there,” she said. “But this is a veteran team, experienced team. They can lock in … their commitment to excellence even if you struggled one quarter. They’re always encouraging each other.”

After falling behind by 13 points after a Reese layup with six minutes left in the second quarter, the Liberty regrouped and orchestrated a 9-0 run, ending with a Fiebich feed to Jones inside for two points, to force a Chicago timeout with the game back within four points with 4:05 left in the half.

In the final seconds of the half, Chicago’s Carter sprinted into the paint but Jones blocked her shot to end the half with the Sky leading, 40-38.

The Carter drive was a rare sight for the remainder of the game, as the Liberty made defensive adjustments to keep the guard out of the lane.

“I think we gave her too many direct drives early,” Brondello said. “So, we just tidied that up. Rim protection got better. I think J.J. [Jones] had a fantastic game tonight. Just that rim protection there.”

The stronger defense led to more offense, with the Liberty scoring 21 points off of Sky turnovers.

Once their 13 3-pointers started to fall, it was enough for the Liberty to go to their eighth win in their past 10 games.

“They were continuing to lift us up,” Ionescu said about the massive Barclays Center crowd. “We need them. We need their support all year long. We were on a back-to-back. If they came out and kind of were dead, we might have been too. But I think being able to see how committed they are to wanting to watch us play, we don’t take any of these moments for granted. We understand what a blessing it is to be able to play at home in front of 17,000 fans.”