The Washington Redskins regretted letting Ryan Clark get away long ago. It took eight years, but they finally brought him back by agreeing to a one-year deal, according to sources.

On Monday night, Clark took to Twitter to thank the Steelers.

Enjoyed every second of the last 8 years in Pittsburgh. Great city, amazing organizations & of course awesome fans! Thank you Steeler Nation - Ryan Clark (@Realrclark25) April 1, 2014

Pittsburgh opted not to re-sign Clark, 34, instead choosing another free agent, Mike Mitchell. The Redskins were interested in Mitchell as well, but turned to Clark shortly after losing out on the former Carolina Panthers. Clark, temporarily at least, fills a gaping hole for the Redskins -- one that has existed since Sean Taylor died in 2007.

Clark started alongside Taylor in 2004-05, but left via free agency to join Pittsburgh in 2006. Clark also is considered a strong mentor, which the Redskins hope helps develop some of their younger safeties such as Bacarri Rambo and Phillip Thomas, or a draft pick in May.

It also helps that the Redskins play a similar system as Pittsburgh, easing Clark's transition. Clark agreed to a deal just as receiver DeSean Jackson arrived in town. He's expected to dine with Redskins coaches Monday night and have his formal visit Tuesday.

After the Redskins let him leave following the 2005 season, the Steelers struck gold with Clark. He provided them with an eight-year starter at free safety as well as an anchor in the secondary. Clark, who made the NFL as an undrafted free agent, played out two contracts in Pittsburgh, but it became apparent during the 2013 season that he wouldn't receive a third deal from the team.

Clark was solid in run support -- he finished second on the team with 102 tackles -- but he simply couldn't cover ground the way he had in recent years, and the Steelers need an injection of youth in their secondary.

Clark, 34, played in the shadow cast by strong safety Troy Polamalu but he also thrived while paired with the eight-time Pro Bowler. The two became close friends, and Clark's presence at free safety allowed the Steelers to move Polamalu all over the field, making it difficult for opposing offenses to account for him.

A fearless hitter, Clark twice recorded over 100 tackles in a season for the Steelers. He intercepted 12 passes in Pittsburgh and served as a team captain in 2013.

ESPN.com Steelers reporter Scott Brown contributed to this report.