Hasselbeck has completed 59.9 percent of his passes this season for 3,001 yards and 12 touchdowns, with 17 interceptions.
Whitehurst, who has appeared in six games this season, completed 22 of 36 passes for 192 yards and a touchdown against the Rams. The 16-6 win handed the Seahawks (7-9) an improbable NFC West title and a home playoff game against the defending Super Bowl champion Saints (11-5).
And Saturday could be the last time Hasselbeck plays for the Seahawks.
"As we saw this year with the amount of turnover we had, you never know when your last day could be and that goes for everybody," Hasselbeck said. "I'm excited. Anybody who has played here when the crowd is really into it, it's always a lot of fun. Hopefully we can keep that rolling."
Hasselbeck's contract with the Seahawks expires at the end of the season. He repeated on Thursday a desire to retire in Seattle. After 10 seasons, 147 regular and postseason games appeared in and the only NFC championship the club has ever claimed, Hasselbeck could be on his way out.
Hasselbeck's future was placed in doubt the moment Seattle traded a second-round pick to San Diego and signed Whitehurst to an $8 million, two-year contract. The move was part of Carroll's constant refrain of competition being at the center of everything the Seahawks do, and while Whitehurst failed to win the job during training camp and has only seen spot duty this year, the move was a signal that Hasselbeck's future beyond 2010 in Seattle wasn't guaranteed.
Hasselbeck will turn 36 in the first month of next season.
By playing on Saturday, Hasselbeck can at least ensure the potential final image of his career in Seattle isn't watching him score on a 1-yard touchdown run in Tampa Bay the day after Christmas, then going to a knee in the end zone after aggravating his hip injury. Hasselbeck wasn't touched, wasn't even threatened by a defender on the play -- his third rushing TD of the season, a new career high.
"For me the most special thing was coming here, we really weren't a very good team. It was hard to get this thing turned back around and get something special built here," Hasselbeck said. "So I take so much pride in that and for the opportunity I was given.
John Clayton is a senior NFL writer for ESPN.com. The Associated Press contributed to this report.