The Sixers' championship hopes could have a lot to do with how Ben Simmons, Joel Embiid and Tobias Harris perform in the upcoming postseason.

But Simmons left the third quarter of Wednesday's 107-98 win against the Washington Wizards at The Arena with a left knee injury and did not return.

Simmons grabbed an offensive rebound with five minutes, 53 seconds left in the third quarter. He dribbled to the corner before throwing an outlet pass to Al Horford.

The two-time All-Star then flexed his left leg, grabbed his hamstring and walked off the court. He gingerly walked back to the locker room, followed by general manager Elton Brand.

Coach Brett Brown said after the game the team didn't know anything on the extent of the injury.

"We don't know," Brown said. "I'm sure the club will make some announcement. But as far as knowing more than that, I don't. Obviously I'm very curious."

Yahoo Sports reported Simmons didn't experience any swelling or pain in his knee. This was his third game back after missing the final eight games before the NBA shutdown in March with a pinched nerve in his lower back.

On Wednesday, Simmons had eight points on two-of-10 shooting to go along with six rebounds, four assists, two steals and two turnovers in 22 minutes, 55 seconds.

The Sixers moved Simmons from point guard to power forward during the restart.

Shake Milton became the full-time starting point guard in the process. Simmons looked good in his new role in three preseason games but struggled on the defensive end in the Sixers' first two seeding games.

On Monday, Simmons recorded eight points and five assists, but he never got into the flow because of foul trouble. Simmons fouled out with 2:12 remaining.

It appeared that things would be better for him early in Wednesday's game.

There's been discussion about Simmons not attempting a three-pointer after making one of two in the Sixers' scrimmage opener against the Memphis Grizzlies on July 24.

It didn't take long for him to hoist one Wednesday.

His second attempt of the game was a missed seven-metre corner three-pointer, one minute and 39 seconds into the contest.

Simmons handled the ball more as a point-forward against the Wizards. That led him to being more active. He attempted two of the Sixers' first four shot attempts en route to scoring five points on two of six shooting in the first quarter. The Australian only had six total shots on Monday against the Spurs.

On Wednesday, Philly went into the second quarter leading 26-20 after Milton's three-pointer before the first-quarter buzzer.

But at the 5:14 mark of the second quarter, Simmons showed why he's at his best with the ball in his hands.

The 2.08-metre star had a mismatch with former Sixer Ish Smith guarding him. Simmons backed Smith up, drove the lane and fired a pass to a wide-open Josh Richardson, who buried a three-pointer to put the Sixers ahead 41-36.

Philly went on to build a 10-point cushion and the Sixers (41-27) eventually went on to win by nine points.

The Sixers' next game is on Friday against the Orlando Magic.

Australian Associated Press