Simon, a fifth-round pick, was dealing with a knee issue last week. He was taken off of the injury report on Friday but then was inactive in Week 1 against the Miami Dolphins.
Coach Pete Carroll had raved about Simon's play in the summer. He was expected to give the team depth as its fourth cornerback. Simon dealt with various injuries throughout his career and played in 11 games (five starts) in three seasons.
Thorpe (6-foot-1, 200 pounds) spent the last two seasons with the Oakland Raiders. He appeared in 28 games and started two. Originally an undrafted free agent out of Auburn, Thorpe spent 2012 with the Kansas City Chiefs and was active for nine games.
The Seahawks are a bit thin at cornerback. Their starters are Richard Sherman, DeShawn Shead and Jeremy Lane. Behind those three, the team has DeAndre Elliott, a rookie undrafted free agent, and Thorpe.
Meanwhile, Carroll indicated that Tukuafu would be back with the team after getting cut earlier this month. He appeared in 23 games with the Seahawks in 2014 and 2015 and will assume the role of first-team fullback.
The Seahawks also made tweaks to their practice squad, adding defensive lineman Tylor Harris, quarterback Jake Heaps and offensive tackle Michael Ola. The team let defensive lineman Justin Hamilton, wide receiver Kasen Williams and wide receiver Rodney Smith go to make room for the practice squad additions.
It's worth noting that the team did not add a veteran quarterback. Carroll said he expects Russell Wilson (sprained ankle) to play Sunday vs. the Los Angeles Rams, and for now, the team is content going with Trevone Boykin as Wilson's backup.