3 Reasons behind Indiana Pacers wild In-Season Tournament win vs. Boston Celtics

Following a rare Tyrese Haliburton-less win on Saturday against Miami, the Indiana Pacers and their neon and yellow court welcomed the East-leading Boston Celtics to Gainsbridge Fieldhouse in the first In-Season Tournament knockout game.

While this matchup did seem a bit unfair, as Indiana went undefeated in group play and still had to face the best team in the East, hopes were high going into this one from Pacers fans, as Tyrese Haliburton would make his return to the lineup following some upper respiratory issues.

His return would be very much needed, as Indiana did not fare very well in their only other Boston matchup so far this season, losing by 51 points on a night where Tyrese Haliburton sat out, and the Pacers could not contain Boston on offense nor score on them on defense.

Monday night was a different story.

With Haliburton fresh after getting three days of rest, he took on the bright lights of the In-Season Tournament and a national TV spot on TNT. Haliburton and the Pacers came to play, miraculously coming away with a win on the first-seeded Celtics after pulling away in the final moments.

This win means the Pacers advance to the Tournament Semifinals and will play the winners of Tuesday's Milwaukee vs New York matchup. Indiana also has two days of rest before this game, as their semifinal matchup will be on Thursday, December 7.

In what was perhaps Indiana's best win of the season, there were a lot of factors and key contributors that stepped up. Let's take a look at those factors right now.

1. Offensive firepower on the right night

Everyone knows the Pacers can score. Everyone knows the Pacers will most likely score. However, doubts have been cast about their scoring since the Orlando Magic game a few weeks back.

In that game, the Magic, the league's best defense at the time, held the Pacers to a shell of what they usually are and smothered them on defense en route to victory.

Before the Boston matchup, there were talks that the same would repeat itself, with the Celtics currently having the second-best defense in the league, holding opposing teams to just 108 points and holding the Pacers to a season-low 104 points the last time they matched up.

However, the Celtics had not accounted for Tyrese Haliburton, apparantly, as his addition gave Indiana a much-needed scoring and distributing boost.

While Haliburton was fantastic at putting the ball in the basket on the night, scoring 26 points, he would not be at it alone. Once again, the scoring load was shared in Indiana, as seven Pacers landed in double figures on Monday.

Alongside Haliburton, Buddy Hield scored in the 20s, dropping 21 on the night. Myles Turner and Bennedict Mathurin assisted as well, scoring 17 and 16, respectively, and Obi Toppin, Aaron Nesmith, and Bruce Brown also scored in double-figures, scoring 12, 14, and 13, respectively.

Indiana has characterized themselves this season by their uptempo offense and ability to score at will, and Monday was no difference. They have proved that they can do it against any defense, and they proved that against the Celtics.

2. Defensive improvements

Of course, the Pacers scoring a lot of points seemed like a formality. Win or lose, Indiana usually manages to fill up the stat sheet with gaudy scoring numbers. The main factor behind Indiana's win on Monday, however, was their defense.

It's no secret that the Pacers aren't known for their defense, which has been seen as the weakest part of the team so far. Nineteen games into the season, Indiana has traded flashes of defensive potential with the usual low effort and lack of motivation on that side of the floor.

Monday was different, however. While Boston shot 47.4% from the field on the night, a decent percentage, they only shot 29.3% from beyond the arc, a remarkably low number compared to how they usually shoot.

The third quarter was particularly frustrating for Boston, as they only shot 41% from the field and 30% from three, scoring 23 points, while Indiana gained control of the game with 37 points of their own, taking a seven-point lead that they would eventually capitalize on with a win.

The defensive heroes of the night were Myles Turner, Bruce Brown, and Aaron Nesmith. Being one of the few legit big men on the team, Turner certainly showed it on the night, grabbing 10 rebounds despite usually being left at a rebounding disadvantage due to the Pacers' lack of size, and getting a steal. Speaking of steals, Bruce Brown had three of them on the night, which led to some fast break points.

Despite this, perhaps the biggest defensive contributor of the night was Aaron Nesmith. While his stats don't jump out the screen, with only a block to his name, Nesmith's hustle in drawing offensive fouls and going for every ball was key in Indiana pulling away late.

On this night, along with a few nights before this, the Pacers showed, once again, that they are not a lost cause on defense, as they slowed down one of the league's best offenses while capitalizing on every mistake made by Boston.

3. Tyrese Haliburton leads late-game heroics

While all of this is fine and dandy, the Pacers were still in a dogfight in the fourth quarter, with Boston chipping away at the lead and eventually taking one of their own to put the Pacers on the brink of elimination. Boston would go as far as to tie the game at 105 apiece with less than two minutes remaining. This is when Indiana would wake up, however, with the Pacers going on a 14-7 run to end the game and not looking back.

The run would be started off in poetic fashion, as Tyrese Haliburton did what Tyrese Haliburton does best and converted a four-point play to put Indiana up four with just over 90 seconds remaining, a shot that must have sucked the life out of Boston.

Indiana would not be done, as following a miss on the other end by Jayson Tatum, Buddy Hield would continue to pile it on with a deep three-pointer to put Indiana up seven with under a minute to go. This shot had Troy Pepper, the Pacers PA announcer, out of his seat.

Following this three was when things started looking bleak for Boston, as Derrick White's bad pass was picked off by Myles Turner, leading to an Aaron Nesmith dunk that nearly tore the roof off Gainsbridge Fieldhouse, bringing back memories of old playoff moments.

This dunk would cap off a 9-0 run by Indy to snatch the game away from Boston, as with 30 seconds left and a nine-point deficit, there wasn't much the Celtics could do at this point. Jayson Tatum's layup put the game within seven, but some Indiana free throws would put the game away for good, along with a Buddy Hield three-pointer at the buzzer to rub salt in Boston's wound.

Overall, Indiana would outscore Boston 37-34 in the fourth quarter to take the game and shoot 54% from the field and 50% from three en route to a 112-122 victory.

With this resounding win, the Indiana Pacers are headed to the semifinals in Las Vegas, where they will either face the Milwaukee Bucks or the New York Knicks, depending on who wins Tuesday's quarterfinal matchup.

No matter who they face and how they fare in the upcoming game and possibly the one after that, the Pacers have to feel good about getting this far. So far, they have gone 5-0 in group play as well as knockout round play, and they seem prime for the big moments.

This game is the biggest stage that many of these players have been on, including Tyrese Haliburton, and they have risen to the occasion. We'll see what else they have in the tank come Thursday.