Because the Steelers have a policy of not negotiating during the regular season, Keisel is expected to be the final player signed before the Sept. 10 opener against Tennessee. Keisel was to have made $3.25 million in the final year of his contract this season.
Terms of a deal that runs through the 2013 season, when Keisel turns 35, were not immediately available.
While Keisel doesn't accumulate a lot of sacks in the Steelers' 3-4 system -- he had one last season and has 11½ in his six-season career -- he is considered to be a key to what statistically was the NFL's top defense the last two seasons.
"It is no secret he is our kind of guy," coach Mike Tomlin said Monday of Keisel, a seventh-round draft pick in 2002. "He is always prepared and he is a great teammate."
Keisel's first career postseason fumble recovery came on Arizona's final offensive play of the Steelers' 27-23 victory in the Super Bowl on Feb. 1.
"He is ridiculously competitive," Tomlin said. "He has a mean streak, if you will, something that's necessary, that comes with playing the position he plays. He takes a great deal of pride in his work. He doesn't care who gets the credit. A lot of times, particularly when you play defensive end in our scheme, you know it's a lot of dirty work: occupying blocks, creating opportunities for others such as James Harrison and LaMarr Woodley, who benefit greatly from the work of our ends."
The other Steelers defensive end, Aaron Smith, is signed through the 2011, which means first-round draft pick Ziggy Hood might not move into the starting lineup for a couple of seasons, unless there is an injury. Hood, from Missouri, has had a strong first training camp.
"That (speculation) could go on endlessly," Tomlin said. "Let's just see how it pans out. I hadn't begun to think about that. I'm just glad they're on our team."
The Steelers likely will play the season with six key players unsigned past 2009: running back Willie Parker, nose tackle Casey Hampton, right tackle Willie Colon, safety Ryan Clark, center Justin Hartwig and kicker Jeff Reed.
The Steelers previously signed linebacker James Harrison, guard Chris Kemoeatu, left tackle Max Starks, right guard Trai Essex, tight end Heath Miller, wide receiver Hines Ward and linebacker Keyaron Fox.
Tomlin, as expected, said the starters will play only a series or two in Thursday's preseason game at Carolina. The offensive starters played the first half of the 17-0 win over Buffalo on Saturday, while the defensive starters played one series into the third quarter.
"There's no question that their experience will be a short one," Tomlin said. "That's the nature of it. They have some teammates who are fighting to the bitter end to play well and make this team. Those guys understand that. They are sensitive to that. They're going to be supportive of those guys."