San Antonio Spurs forward Tobias Harris will miss the entire preseason after suffering a strained left calf during training camp, leaving his availability for the start of the regular season uncertain.

Harris, who joined the Spurs as a free agent on July 6, was unable to take part in the team’s annual Silver & Black intrasquad scrimmage on Sunday because of the injury.

The 6-foot-8 power forward is expected to remain sidelined throughout San Antonio’s five-game preseason schedule. He will be reevaluated after those games before the team determines whether he is ready to return to action.

Team officials have listed Harris as questionable for San Antonio’s regular-season opener against Oklahoma City on Oct. 20. The game will be a rematch of last season’s Western Conference Finals, adding extra significance to the Spurs’ opening fixture.

Harris’ injury means San Antonio will have to prepare for the new campaign without one of its offseason additions during preseason.

The veteran forward signed a two-year contract with the Spurs after spending the previous two seasons with Detroit.

Last season, Harris averaged 13.3 points, 5.1 rebounds and 2.5 assists while playing 27.7 minutes per game. His performances helped Detroit finish at the top of the Eastern Conference standings.

His arrival in San Antonio provided the Spurs with another experienced option in the frontcourt, but the calf problem has interrupted his preparations with his new team.

With Harris unavailable for preseason action, his recovery will now be monitored ahead of the Oct. 20 opener. The post-preseason reevaluation should provide the Spurs with a clearer indication of whether he will be able to make his regular-season debut against Oklahoma City or require additional recovery time.

For now, San Antonio will go through its five preseason games without Harris as the forward focuses on recovering from the injury and becoming available for the beginning of his first season with the Spurs.