ATLANTA — Ben Simmons will miss his second straight game for the 76ers after experiencing knee stiffness Thursday in a loss to the Brooklyn Nets.

The All-Star did not fly with the Sixers to Atlanta on Sunday for Monday’s game against the Hawks. The Sixers held Simmons out of Saturday’s 115-103 home loss to the Denver Nuggets because of knee stiffness.

The fourth-year veteran is averaging 13.4 points, 8.8 rebounds, and 7.0 assists in nine games. Simmons had season highs of 17 points and 12 assists against the Washington Wizards on Wednesday. Four days before that, he posted a triple-double against he Charlotte Hornets, finishing with 15 points, 12 rebounds, and 11 assists.

Simmons had 11 points, four rebounds, and two assists in 31 minutes, 37 seconds against the Nets on Thursday.

His injury does not come at a good time. The Sixers are already without Seth Curry, Tobias Harris, Shake Milton, Matisse Thybulle, and Vincent Poirier because of the NBA’s COVID-19 protocols. Curry tested positive for the virus. Harris, Milton, Thybulle, and Poirier are out because of contact tracing. The four players sat a table with Curry during a team meeting on Thursday.

The Hawks (4-5) are riding a four-game losing streak. After Monday, the Sixers will face the Miami Heat in a “baseball-style” two-game series Tuesday and Thursday at the Wells Fargo Center.

The NBA implemented these series as a way to cut travel during the pandemic. Teams play two consecutive games in the same city against each other on back-to-back nights or over three days.