Pittsburgh opted to sign Clancy to a one-year contract instead of former Steelers defensive tackle Oliver Gibson. Details were not yet available, but Clancy likely signed a one-year deal for the minimum base salary of $535,000, prorated over the rest of the season.
Hampton, who suffered ligament damage to his right knee in a victory Sunday at Dallas, was placed on injured reserve and will need surgery.
Backup safety Mike Logan also was placed on injured reserve, ending his season. The eight-year pro, a valuable backup at both safety spots, suffered a hamstring injury in the Oct. 10 game.
Clancy, 26, played four seasons with the Steelers before his release this summer. He appeared in 42 games, with six starts, and totaled 22 tackles. The former Mississippi standout, a third-round pick in the 2000 draft, will back up Chris Hoke, who will start in place of Hampton.
Ironically, the little-used Hoke, who had never played in a regular-season game before this year, beat out Clancy in camp for the backup job to Hampton.
Steelers coaches also could use defensive end Kimo von Oelhoffen at nose tackle. But the hope is that Hope and Clancy can serve as worthy replacements for Hampton, a Pro Bowl performer in 2003.
Pittsburgh has a bye this week and will resume play Oct. 31 when it hosts New England. The off-week will provide Steelers coaches additional time to work with Hoke and to get Clancy back into football condition.
The loss of Hampton, who is said to have been distraught by the injury following the Steelers' fourth straight victory, is a major setback for a defense that statistically ranks No. 5 in the NFL. Pittsburgh is already playing without starting inside linebacker Kendrell Bell, who has suffered a series of injuries, and who recently underwent hernia surgery.
The team's first-round choice in the 2001 draft, Hampton is a key to the team's defense versus the run, a player whose value typically is not indicated by total tackles, but who anchors the interior of the Pittsburgh 3-4 front. The former University of Texas standout started the first six games of the season and had 21 tackles.
Cornerback Chad Scott, hurt in Sunday's game, is expected
to miss four to six weeks with an injured quadriceps tendon.
To replace Logan, the Steelers signed five-year veteran Tyrone Carter, who has played with the Minnesota Vikings and New York Jets. In 62 games, including 31 starts, Carter has 230 tackles, three interceptions and one sack. He has also averaged 21.7 yards on 34 kickoff returns.
Len Pasquarelli is a senior NFL writer for ESPN.com. To check out Len's chat archive, click here.