The team announced on Monday that McInnis has torn cartilage in the knee.
McInnis suffered the injury in a 110-77 loss at Dallas on Saturday, capping a 1-3 road trip for the Nets.
New Jersey did not have starting forward Richard Jefferson for the last three games of the trip -- losses to San Antonio, Memphis and Dallas -- because of back soreness.
After not playing at all in six of 12 games, McInnis scored six points in 12 minutes in the loss at Memphis on Friday and played five minutes before being injured in Saturday's game at Dallas.
McInnis, 31, is averaging 5.3 points and 1.9 assists in 28 games this season. He averaged 12.8 points and 5.1 assists in 76 games last season with the Cleveland Cavaliers.
A second-round pick out of North Carolina in 1996, the 6-4 McInnis has played for five NBA teams. He averaged a career-high 14.6 points for the Los Angeles Clippers in 2001-02.