The severity of Duncan's condition isn't yet known, but Wednesday night would mark his third absence in San Antonio's past four games. The Spurs held Duncan out of the team's 120-90 loss to the Golden State Warriors on Monday, and he also missed Thursday's win over the Phoenix Suns before returning to the lineup for a 108-95 win on Friday over the Los Angeles Lakers.
Duncan traveled with the Spurs to Oakland, California, to face the Warriors, but the team sent him back to San Antonio to nurse the injury.
Spurs coach Gregg Popovich divulged little information before Monday's game regarding Duncan's knee, but the condition isn't believed to be serious.
With Duncan out of the lineup against the Warriors, David West filled in as the starter, contributing 12 points and five rebounds in 19 minutes.
West will likely be in the starting lineup again Wednesday night against the Rockets.
In his 19th NBA season, Duncan, 39, has played in 37 games, averaging 8.9 points. When the Spurs host the Rockets at the AT&T Center, Duncan will have played in only one game in a span of 10 days.