Darren Yamashita-USA TODAY Sports

The San Francisco 49ers signed quarterback Brandon Allen in May. The move was just the addition of another camp arm for those outside looking in. And it sounds like that's what it started as. However, the veteran quarterback has impressed head coach Kyle Shanahan and the 49ers.

"We knew in free agency we didn't know where Brock was going to be at the time, so we knew we had to go get someone to compete with [QB] Trey [Lance] in case Brock wasn't [healthy]," Shanahan told reporters after Tuesday's practice when asked about Allen. "And we got fortunate with [QB] Sam [Darnold] on that.

"Then we felt good just with our targets and everything, and once we kind of started phase one, when we're doing all the quarterback drills and workouts and stuff, it was just, 'Man, there's only two quarterbacks here. Brock can't do much, and we would like a third guy.' And then we looked out there, and [Allen] was available.

"And then he had the confidence to come here. And when we watched his tape, and we've always known about him, we felt very fortunate to get him because he has been a backup in this league. So when he came here and hopped in our drills, I think we got like two weeks with him, and I've been extremely impressed. The reps he's gotten, he's done very well."

While it seems unlikely Allen will make the 53-man roster if Purdy, Lance, and Darnold are all healthy, the 49ers don't necessarily view Allen as just a "camp arm."

"He's obviously not just a camp arm around this league," Shanahan said. "He's been a backup for a while. Just how good he's done, and his OTAs and stuff is going to give him a chance with us."

Shanahan won't dismiss the possibility of all four quarterbacks remaining with the 49ers this season.

"Technically, the fourth guy was number two for Cincinnati the last couple of years, and that's the way he won it," Shanahan said. "We could have gone the college free agent route, but when we looked into those guys, compared to what was out there, the fact that Brandon was willing to do it, we would never hesitate to do that.

"Now, if someone like Brandon doesn't want to do it, and other guys that you think are NFL caliber don't want to do it, that is when you go the college free agent route. But we feel our guys are much better than those options."

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