San Francisco 49ers rookie quarterback Kurtis Rourke is benched in Thursday's NFL preseason game against the Los Angeles Chargers after he sustained a rib injury in the team's opener against the Tennessee Titans.San Francisco 49ers rookie quarterback Kurtis Rourke is benched in Thursday's NFL preseason game against the Las Vegas Raiders after he sustained a rib injury in the team's opener against the Tennessee Titans. ((AP Photo/Kelley L. Cox) and Luke Hales/Getty Images/AFP)His absence has drawn attention to Adrian Martinez, who is filling in as one of the team's three quarterbacks alongside Brock Purdy and Mac Jones.Before kickoff, reporter David Lombardi posted on X that Purdy was in full uniform for the first time this preseason and that he, Jones and Martinez were the three quarterbacks available for the game.Why is Kurtis Rourke out?Rourke's absence comes less than two weeks after an impressive NFL preseason debut that ended prematurely because of injury.The former Indiana quarterback completed 12 of 14 passes for 101 yards against the Titans. But in the second quarter, he sustained a rib injury that limited his playing time. Subsequent testing reportedly showed that Rourke did not suffer a broken rib, but the team has remained cautious with his recovery after he complained of breathing issues. There is still no confirmed timeline for his return to game action.On Sunday, coach Klay Kubiak praised the rookie Canadian player's game and said, “I mean, he's a really young player who's got a bright future with a lot of room to grow, but that is why we drafted him, is we thought he was an NFL quarterback.”According to Athlon Sports, Kubiak added that although Rourke was superior to a seventh-round selection, teams were aware that he would likely be unable to play as a rookie due to an injury sustained in college.He said, “We saw a guy who was an NFL thrower, who was very bright, who had the right size and who had the chance to be a player. We still think he is. And I think he's taken steps in that direction, but he's got to keep going.”(This story is being updated)