Cooper Rush will start at quarterback in the Atlanta Falcons’ season opener on Sunday in Pittsburgh after Tua Tagovailoa was ruled out with an oblique injury.

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Rush only signed in Atlanta on July 29, the opening day of training camp, after injuries left the Falcons without any of their top three quarterbacks, and it’s an injury that has elevated Rush to the start this week. Atlanta had planned to start Tagovailoa, who signed a one-year deal in March, but Tagovailoa hurt himself early in Thursday’s practice while participating in a throwing drill.

Rush had only one series with the Falcons’ starters during training camp, he said, but took all of Atlanta’s first-team reps Thursday and Friday.

“In an ideal world, would you love to have gotten every rep? Of course, that’s a no-brainer,” head coach Kevin Stefanski said Friday. “Cooper has been a backup. He’s been a starter. He knows how to prepare.”

Rush began his NFL career as an undrafted free agent with the Cowboys in 2017. He spent seven seasons as a backup in Dallas, compiling a 9-5 record in 14 starts. He played for the Ravens last season, starting two games and losing both of them. He clearly welcomes this opportunity.

“Every throw you throw to Drake (London), every throw you throw to Kyle (Pitts) matters,” Rush said. “The game prep doesn’t change mentally. I think that’s been an advantage of mine. I’ve always kind of kept it the same whether I am starting or not. Where things change is if you’re starting, you’ve got to talk with those (starting) wideouts, the O-line, ‘How’s the cadence?’ That type of stuff.”

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The 6-foot-3, 224-pound Central Michigan alumnus played in all three Falcons preseason games, finishing a combined 30-for-48 for 254 yards, a touchdown and two interceptions. He has thrown for 3,766 regular season yards with 20 touchdowns and 14 interceptions.

He was working out at a gym in his hometown of Dallas when the Falcons called in July, he said.

“Kind of out of the blue they called the first day of camp, and it worked out,” he said. “I was happy about that. Good spot, good organization, good staff. I was happy and pumped.”

Tagovailoa was named the starting quarterback Monday after competing with Michael Penix Jr. for the job throughout camp. Penix told the Falcons coaching staff last week that he didn’t feel physically ready to play in a game yet after rehabbing a torn ACL throughout the offseason, Penix said. Penix was cleared for 11-on-11 practice work on Aug. 24 but did not appear in any preseason games.

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Penix will be inactive for Sunday’s game, Stefanski said Monday.

This article originally appeared in The Athletic.