Losing his starting quarterback is anything but an ideal situation for Jeff Fisher, but the St. Louis Rams coach is taking it in stride -- just as he did last season when the dilemma presented itself.

With Sam Bradford's injury and the Minnesota Vikings' decision to start Matt Cassel under center, Sunday's season opener in St. Louis will instead be a battle between former undrafted free agents rather than one between first-round picks.

Shaun Hill, a 13-year veteran who hasn't started in more than three years, will take the reins for the Rams as they meet a Vikings team that still revolves around Adrian Peterson and its cohesive offensive line.

Bradford tore his left ACL against Carolina on Oct. 20, and the Rams went 4-5 the rest of the way with Kellen Clemens starting and would finish with seven wins for the second straight season under Fisher.

The No. 1 overall pick in 2010 then tore the same ACL in a preseason game Aug. 23, leaving Fisher to again turn to a veteran backup with limited starting experience. He doesn't seem too worried, though.

"I feel really good," Fisher said. "We're ready to play. We've got a young team once again, but we've got a team that has a lot of confidence in itself -- and our starting quarterback as well."

Hill, who began his career in Minnesota from 2002-05 after signing as an undrafted rookie, has been in this situation before. He started 10 games for Detroit in 2010 when Matthew Stafford suffered a shoulder injury.

"Life of a backup, you might not go in for a few years, but you have to stay ready," Hill said. "This is not anything new, it's not anything different. I keep the same mindset I've always had."

Cassel also wasn't drafted and got a break in his career with New England in 2008 when Tom Brady suffered a season-ending injury in Week 1. After having some success in Kansas City, he was one of four quarterbacks to start a game for Minnesota during its 5-10-1 campaign last season.

The Vikings drafted Teddy Bridgewater with the last pick of the first round as their quarterback of the future, but Cassel impressed first-year coach Mike Zimmer and new offensive coordinator Norv Turner enough during camp to win the job.

"I've been through a lot in my career," Cassel said. "I've been through the ups, I've been through the downs. I've been through the highs and the lows. At this point nothing really surprises me in my career. Because of those (experiences), it callouses you to a few different situations that as a younger player I might not have taken it as well."

Cassel has some good weapons to throw to in emerging second-year receiver Cordarrelle Patterson and veterans Greg Jennings and Kyle Rudolph, but Peterson will remain the workhorse if he stays healthy.

After rushing for the second-most yards in NFL history in 2012, Peterson dealt with multiple small injuries and a sprained right ankle that forced him to miss two games in December last season. He still rushed for 1,266 yards, fifth-most in the NFL, but it was the second-fewest of his career to the 970 he gained in 12 games before tearing his ACL in 2011.

"It's very important to me to make sure that I'm doing the small things, keeping my body healthy and making sure I make it through the entire season," Peterson said. "I feel pretty good about our chances. I feel like we have all the pieces."

He'll be running behind a familiar offensive line as the group of Matt Kalil, Charlie Johnson, John Sullivan, Brandon Fusco and Phil Loadholt will be the same that has started the past three seasons.

"We're a tight-knit group," Kalil said.

That line will be up against an imposing defensive front for Rams, who boast former first-round picks Michael Brockers, Chris Long and Robert Quinn. Their depth on the defensive line led to the release of seventh-round pick Michael Sam, the first openly gay player to be drafted.

Peterson, though, busted through that same line for 212 yards and a touchdown Dec. 16, 2012, in Minnesota's 36-22 win the last time these teams played.

The Rams boast a solid running back of their own in Zac Stacy, who rushed for 973 yards and seven touchdowns in 14 games as a rookie last season, and he should carry the load this year.

Fisher, though, may elect to go to the air a bit more in this contest, as the Vikings defense allowed the most touchdown passes (37) and second-most passing yards per game (287.2) in 2013.

Zimmer, the former Cincinnati defensive coordinator who took over for the fired Leslie Frazier, is hoping the success Minnesota had with his new schemes in the preseason will carry over.

"Keep doing the things that we've done in the preseason, we can go out and beat anybody," Zimmer said. "But we have to go out and do them. We can't talk about it."

The Vikings signed former Giants defensive tackle Linval Joseph to a five-year, $31.25 million contract in the offseason, but he was hit in the leg by a stray bullet after the preseason opener. He's on track to play Sunday after returning to practice this week.

Minnesota's offense will be shorthanded, though, as receiver Jerome Simpson will serve a three-game suspension for violating the NFL's substance abuse policy for the second time.