RENTON, Wash. -- When the Seattle Seahawks pursued Bradley McDougald in free agency, they did so with an eye toward protecting themselves against a repeat of what happened last season. All-Pro free safety Earl Thomas went down with a broken leg in December, and their pass defense wasn't nearly the same without him.

After signing McDougald to a one-year deal, the Seahawks felt they were better equipped to replace Thomas in the event that he was injured again.

That contingency plan will be put to the test now that Thomas has a hamstring injury that will elevate McDougald into a starting role Sunday against the Washington Redskins (3-4) at CenturyLink Field.

"We’re really, really fortunate," coach Pete Carroll said. "Bradley is a ... front-line guy that has played a lot of football for us in and out and has done a ton of stuff. He’s smart, he’s a leader, he’s tough and all of that. Him coming off the bench to fill that spot, we’re very fortunate.”

Carroll's talk of Seattle feeling fortunate isn't just coachspeak. The Seahawks legitimately felt they got a steal when they signed McDougald, 26, to a one-year deal that included $750,000 guaranteed and a max value of $2 million with incentives.

He had started 31 games over the previous two seasons with the Tampa Bay Buccaneers, who went in a different direction when his contract expired. That starting experience was something the Seahawks didn't have last season when Steven Terrell had to step in for Thomas, first because of a hamstring injury in Week 11 and then for the rest of the season when Thomas broke his tibia two weeks later.

Seattle's pass defense sorely missed him. The numbers were staggering.

Seattle allowed 5.96 yards per dropback, 7.01 yards per attempt and a passer rating of 77.8 with Thomas on the field last season, according to ESPN Stats & Information. Without him, those numbers were 6.76 yards per dropback, 7.77 YPA and a 100.3 passer rating.

The Seahawks also allowed 12 touchdown passes with only one interception without Thomas compared to seven touchdowns and 10 interceptions with him.

It wasn't all Terrell's fault, to be sure, but the drop-off supported the widely held belief that Thomas may be more important to Seattle's defense than any of that group's other stars.

The Seahawks signed McDougald to be more than just a backup to Thomas and to Kam Chancellor at strong safety. He's played alongside those two as a third safety in some nickel packages, though only sparingly until Week 7 against the New York Giants. McDougald drew strong reviews from coaches after spending several of his 17 defensive snaps in that game matched up with speedy tight end Evan Engram.

McDougald said it was different at first going from a starter the past two seasons to only occasionally seeing the field on defense for Seattle -- he's also been a regular on special teams -- but he realized it's what he signed up for. And he knew there was a good reason he wasn't starting in Seattle's secondary.

"Look at the guys in front of me," he said.

Thomas had been having another All-Pro-type season before he went down in the fourth quarter last week. Carroll said Friday that he doesn't know if Thomas is in danger of missing more than this week's game; Seattle plays the Arizona Cardinals the following Thursday, which would require Thomas to make a quicker recovery than he'd he have to for a Sunday game.

So McDougald's time in the starting lineup could last beyond Sunday.

"He's ready to play," Carroll said. "He knows everything. He communicates beautifully with our guys and has been on the field a lot, so it really doesn’t feel like newness. You're going to miss Earl just because Earl is Earl, but Bradley will do a really good job.”