After opening the second round of the playoffs with two home wins, the undermanned Celtics aim to take control of the series.

Jim Fenton The Enterprise @JFenton_ent

BOSTON – They arrived at the TD Garden on Monday night as the hottest team in the NBA since the middle of March.

The Philadelphia 76ers had won 20-of-21 games, including 16 in a row to close out the regular season before eliminating the Miami Heat in five games in the opening round of the NBA playoffs.

They had lost back-to-back games only once (Feb. 25 and 27) since the beginning of February and were looked upon as the new favorite to win the Eastern Conference.

All it took was two nights on the parquet floor for the perspective of the 76ers to drastically change.

The sizzling Sixers were stunned twice by the undermanned Celtics and are facing a 2-0 deficit in a second-round series that continues Saturday at the Wells Fargo Center (5:05 p.m., TV: ESPN; radio: WBZ-FM/98.5).

The Celtics were underdogs in not only the series but in both games on their own court because of their health status, but as has been the case all season, they continue to beat the odds.

“It’s kind of funny,’’ said Jaylen Brown after returning from a strained hamstring to play Game 2. “We’ve been getting the same question since the first game of the year (when Gordon Hayward was hurt).

“We’re here in May, still getting the same question. Just play basketball, man. Great coach in Brad Stevens, have a great front office in Danny Ainge and his crew, and we have some really tough, talented guys in this locker room. When you put that together, we have some great success.”

While people are wondering how the Celtics continue to have success despite being without Hayward and Kyrie Irving, and with Brown and Marcus Smart not at 100 percent, the Sixers are back home needing to get back their winning formula in a hurry.

They let a 22-point lead slip away in a hurry in Game 2, and leader Ben Simmons struggled as the Celtics threw a physical style at him with various defenders.

“I mean, we know what we’ve got to correct,’’ said 76ers center Joel Embiid. “We have to be better defensively. Offensively, we got to keep moving the ball, I think. So, we know what we got to do.

“Honestly, I am not too scared because we know what we got to do to win games. (The Celtics) are a very good team, and they’re well coached. We just have to execute our game plan.”

The Celtics are 36-0 when leading a best-of-seven series, 2-0, including the opening round against the Milwaukee Bucks. The Sixers are 0-11 when they dropped the first two games of a best-of-seven series.

Against the Bucks, the Celtics were in a similar situation but lost Games 3 and 4 in Milwaukee and had to go seven games because they were unable to win on the road.

“Play with more poise and composure,’’ said rookie Jayson Tatum when asked how the Celtics can improve on the road. “They are going to make runs and the crowd is going to get behind them. That is always a tough part, but as long as we can stay composed and do what we have to do and try to block out what’s going on outside of the court hopefully we can take care of business.”

The Celtics, who are nine-point underdogs in Game 3 despite the 2-0 series lead, can take a large step toward a second straight appearance in the conference finals by splitting the two games in Philadelphia.

“It’s a group that wants to play the right way, that’s playing hard and I think you can always appreciate that,’’ said Al Horford of the Celtics. “We have a group of guys that want to do the right things, that are committed, and we’re seeing success in that we are trying to play the right way, defending, rebounding, moving the ball.

“There are a lot of things that go into it and we are trying to figure it out. It’s been such an up and down year for our group, but we are just trying to figure it out as we go.”