He left during the second half of Sunday's 27-24 victory over Denver with what the team described as a sprained right knee. Coach Chuck Pagano said Anderson was supposed to have an MRI on Monday.
A third-round draft pick, Anderson won the starting job in training camp and had 28 tackles - tops among all defensive linemen. He also had one sack, two passes defensed and five quarterback hits.
Indy (4-5) has a bye this week and hasn't made a move to replace him yet.
The Colts also waived backup cornerback Tony Carter, who signed as a free agent Oct. 20.
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