Less than a full quarter into his Boston Celtics debut, star forward Gordon Hayward went down with a gruesome leg injury and is now out for the season.

The Celtics, understandably, reeled after the loss of Hayward, losing the opener to the Cleveland Cavaliers and dropping their next game at home to the Milwaukee Bucks.

However, since then, the team has turned a corner, playing much better basketball as they adjust to life without the star forward.

In fact, the Celtics haven't lost since their home opener against the Bucks, reeling off five-straight wins to climb to 5-2 on the season (and getting revenge against the Bucks in Milwaukee in the process).

Coming off a big 108-94 win over the San Antonio Spurs in Boston on Monday night, it's safe to say the Celtics are hitting their stride, but it's also fair to question why.

Here are three of the biggest reasons the Celtics have managed to turn things around after Hayward went down with a devastating injury:

Kyrie Irving has stepped up his all-around game

Irving was brought in to lead the team, and he's done all that and more. Even when Hayward was healthy, this was always going to be Irving's team, and the star point guard hasn't disappointed.

Though he's not averaging the 25.2 points per game that he did in Cleveland last year (he's scoring 21.7 per night), he's affecting games in other ways, dishing out 5.7 assists and grabbing 3.7 rebounds per contest.

Defensively, he's stepped up his game, too, as he currently leads the NBA in steals per game with an impressive 2.4.

Irving is going to have the ball in his hands more often than he did while playing alongside LeBron James in Cleveland, so it has been nice for Boston fans to see that he's making his teammates better instead of simply looking for his own shots.

Jayson Tatum has filled Hayward's shoes

Tatum was in the starting lineup on opening night alongside Hayward and has started all seven games so far as a rookie, so he hasn't replaced Hayward, per se, but his performance has been incredible nonetheless.

Last year with the Utah Jazz, Hayward averaged 21.9 points, 5.4 rebounds and 3.5 assists per night. So far as a rookie, Tatum - the No. 3 overall pick - has scored 14 points, grabbed seven rebounds and dished out 1.7 assists per game.

Those aren't exactly Hayward's numbers, but Tatum has done a pretty solid impression of his new teammate so far.

If he can continue to find ways to affect games, the Celtics will continue to be one of the Eastern Conference's best teams.

Brad Stevens is pushing the right buttons

No one took the loss of Hayward harder than coach Brad Stevens, who was Hayward's college coach when they were at Butler.

However, Stevens hasn't missed a beat without his star forward, adjusting Boston's rotations and diving deeper into the team's bench, with players like Daniel Theis, Jabari Bird and Semi Ojeleye all getting more minutes than anticipated through seven games.

It'll be tough for Stevens and the Celtics to continue their five-game winning streak over the course of the next few games, because after a home game against the Sacramento Kings on Wednesday, Boston travels to Oklahoma City, Orlando and Atlanta.

Still, Stevens has his team playing well now, and as long as Boston continues to pick up more big wins, the Celtics' confidence will only continue to rise.