The Celtics have regained the upper hand in their second-round series with the defending champion Toronto Raptors.

After back-to-back losses wiped out a 2-0 series lead, the Celtics responded on Monday night with an impressive performance in Game 5 at Disney World.

Leading from start to finish and building a 27-point halftime lead, the Celtics took a 3-2 lead in the series with a 111-89 victory over the Raptors.

The Celtics can clinch a spot in the Eastern Conference finals for the third time in four years by winning Game 6 on Wednesday at 6:30 p.m. If necessary, a deciding game would be played on Friday night.

Since Brad Stevens became coach of the Celtics, they have now won Game 5 five straight times when the series was tied, 2-2, with the previous victories over the Milwaukee Bucks, Cleveland Cavaliers, Chicago Bulls and Washington Wizards.

Teams that win Game 5 in a 2-2 series have gone on to win the series 82% of the time in NBA history.

The Celtics, who gave up 17 3-pointers in the Game 4 loss after being stunned on a last-second OG Anunoby 3-pointer in Game 3, responded with one of their best outings in the playoffs.

They were aggressive on defense right from the start, and the offense was balanced and efficient. The Celtics’ lead never fell under double digits after they went in front, 15-5, with 3:42 to go in the first quarter.

Jaylen Brown, who struggled with his shot in Game 4 when he missed his first nine 3-pointers, had 27 points. Brown made 10-of-18 shots, hitting three 3-pointers, to go with six rebounds and three steals.

Kemba Walker, who took only nine shots on Saturday, added 21 points with seven assists and four rebounds.

Jayson Tatum made only 5-of-15 shots but had 18 points, 10 rebounds and four assists.

The two other starters were also in double figures with Daniel Theis going 5-for-5 and scoring 15 points with eight rebounds and two blocks while Marcus Smart had 14 points, seven rebounds and six assists. Brad Wanamaker contributed 12 off the bench.

Fred VanVleet led the Raptors with 18 points while Kyle Lowry and Pascal Siakam were limited to 10 points each. Toronto missed 28 of 40 shots from 3-point land.

The Celtics’ biggest advantage was 30 during the third quarter, and the Raptors got no closer than 17 points (99-82) in the fourth.

After holding a 27-point halftime lead, the Celtics were hit by a 6-0 run by Siakam to start the third quarter, pulling the Raptors to within 62-41 with 9:30 left.

But Walker answered with a drive and Brown made a 3-pointer to push the edge back to 67-41. The Raptors did not get any closer than 22 points the rest of the quarter.

The lead reached 30 on two occasions, first when Brown made a 21-footer for a 79-49 edge and then on a Tatum basket to make it 82-52.

The Celtics took an 87-63 lead into the last quarter and had six players in double figures through the first 36 minutes.

The Celtics were dominant in the first half, building a 62-35 lead at the break as they limited the Raptors to 30-percent shooting with an aggressive defense.

The 27-point halftime advantage was the second largest at the midway point in the playoffs for the Celtics in the shot-clock era (starting in 1955). They were up by 30 on the Los Angeles Lakers in Game 1 of the 1985 NBA Finals.

The Raptors, who scored 31 points in the first quarter of Game 4, struggled at the offensive end throughout the opening 24 minutes.

No Toronto player reached double figures, and after hitting 17 3-pointers on Saturday, the Raptors went 4-for-18 from behind the line. The Raptors shot 30.2 percent from the floor in the first half.

According to stat guru Dick Lipe, the Celtics have held the Raptors to three of the lowest first-half shooting percentages in the NBA playoffs this summer (28.9 in Game 1 and 33.3 in Game 4).