There has been a different mindset at the 76ers practice facility since Monday.

“You get into a very torrid pace the second it’s go time,” coach Brett Brown said Tuesday. “And go time to me started yesterday.”

The Sixers will open their most anticipated season in decades Wednesday night against the rival Boston Celtics at the Wells Fargo Center.

“Then it’s just a sprint to April, kind of,” Brown said of getting to the April 15 regular-season finale against the Charlotte Hornets at home.

But Wednesday’s opener will be special for a squad expected to contend for the NBA title. The Sixers have several new pieces, including shooting guard Josh Richardson and power forward Al Horford.

The game will have an extra meaning for Horford, who will be facing his former teammates. But it also will give the Sixers an early opportunity to see how good they are.

The Celtics could be the towering Sixers starting lineup’s kryptonite. Boston boasts an athletic, small-ball lineup that likes to get out and run. The Sixers struggled with their transition defense in Friday night’s preseason-finale loss to the lowly Washington Wizards. Plus, don’t be surprised if the Celtics combat the Sixers’ height advantage with a zone defense, on occasion. The Wizards had a lot of success implementing a zone defense Friday.

In addition to being a test, this Celtics matchup is a rivalry game. Make that a lopsided rivalry game.

In their last meeting on March 20, the Sixers defeated the Celtics, 118-115, at the Wells Fargo Center for just their fourth victory in the rivals’ last 25 games. Joel Embiid had a game-high 37 points and a career-high 22 rebounds. The two-time All-Star center also made a career-high 20 foul shots in 21 attempts.

Former Sixer Jimmy Butler scored 15 of his 22 points in the fourth quarter, including an 18-foot jumper with 5.5 seconds left to finally vanquish the visitors.

Butler and several other pieces of last season’s roster have been replaced. But the Sixers still want to build off that victory.

“It’s the matchup against Boston,” Embiid said. “The last couple years, it’s been crazy. We’ve had a few good battles. It’s the first game of the season, so we want to come out and set the tone for this upcoming season because we got big goals.”

This marks the third time in five seasons the Sixers will face the Celtics in the season opener. Last season, the squads met at the TD Garden on Oct. 16, 2018. The two teams also competed in Boston on Oct. 28, 2015.