Jared Goff will be the Rams’ backup quarterback for home opener against the Seattle Seahawks

Rams quarterback Jared Goff, who was inactive for the season opener, will back up Case Keenum in Sunday’s home opener against the Seattle Seahawks, Coach Jeff Fisher said Friday.

Goff, the No. 1 pick in the NFL draft, was in a warm-up suit on the sideline during Rams’ 28-0 defeat by the San Francisco 49ers while Sean Mannion served as the backup.

Now Goff is the proverbial “one play away” from making his regular-season debut.

“It’s just prepare the same way every week,” Goff said. “It can happen at any time.

“Obviously, you’re going to support Case, but anything can happen. I’ll be ready if my number’s called.”

After the Rams’ final exhibition at Minnesota, Fisher said Goff was “not ready” to be the backup. He installed Mannion at No. 2 but said he might alternate the backups after the first game.

On Friday, Fisher said Goff was ready to play and excited about the opportunity.

“He’s got some reps throughout the week , so good for him,” Fisher said. “It will be exciting for him knowing he’s just a snap away from going in the game.”

Keenum is coming off a poor performance against the 49ers. He completed 17 of 35 passes for 130 yards, with two interceptions.

Goff said he was informed early this week that he would be the No. 2 quarterback for a game that is expected to draw a capacity crowd to the Coliseum.

“I’ll get a few reps with the ones [each] day, I don’t know how many exactly, but there’s a handful,” he said. “I don’t feel like I need too many to go in there and play right now. I’d love to have as many as possible, but whatever they do is their decision.”

Goff said he had not been a backup since his sophomore year of high school.

After playing in four exhibitions and then watching the opener from the sideline, he is eager to show he can contribute.

“It’s faster, obviously, when the preseason goes to regular season,” he said. “It’s still football, though, just try to keep it simple.”

Quick hits

Rams defensive tackle Aaron Donald, who was ejected from the season opener, was fined $21,269 by the NFL. Donald was fined $12,154 for unsportsmanlike conduct and $9,115 for unnecessary roughness…. In the latest injury report, cornerback E.J. Gaines and receiver Nelson Spruce are out, receiver Pharoh Cooper is listed as doubtful and defensive tackle Michael Brockers and cornerback Lamarcus Joyner are questionable.

gary.klein@latimes.com

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