Three-time Pro Bowl defensive tackle Marcus Stroud, who missed four games earlier this year because of a league-imposed suspension, was placed on injured reserve by the Jacksonville Jaguars on Wednesday afternoon, ending his season.

The seven-year veteran, who along with John Henderson comprises one of the most imposing tackle tandems in the NFL, suffered an ankle injury in last Sunday's victory over Carolina. The team termed the injury a "significant" one, and the prognosis was that Stroud would not be able to return, even for the playoffs.

Stroud, 29, has had chronic ankle problems in the past and during the offseason underwent microfracture surgery, a procedure typically used on knee injuries, to address the issue.

The former Georgia star was suspended four games for a violation of the league's performance-enhancing drug policy. Stroud did not appeal the suspension, and recently said that the positive test resulted from a supplement that he had quit taking.

In nine games this season, Stroud had 22 tackles, three sacks and two passes defensed, but it was obvious he was not often playing to his past performance levels. The same is true for Henderson, who is experiencing a subpar season and has conceded as much.

Stroud was the Jaguars' first-round choice in the 2001 draft.

In 100 appearances, Stroud has 444 tackles, 22 sacks, six forced fumbles, four recoveries and 23 passes defensed.

Jacksonville likely will rotate veteans Rob Meier and Grady Jackson in his spot in the lineup.

Len Pasquarelli is a senior NFL writer for ESPN.com.