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Scott Tolzien (left) has never thrown an NFL pass while Colt McCoy completed nine of 17 pass attempts in 2012. (AP)
SANTA CLARA -- Coach Jim Harbaugh touted the competitions across the board that are taking place on the 49ers' practice fields.
Those roster battles will continue Thursday night when the 49ers open the exhibition season against the Denver Broncos at Candlestick Park.
Colt McCoy, whom the 49ers acquired in an offseason trade with the Cleveland Browns, entered camp as the presumptive No. 2 behind starter Colin Kaepernick. But Harbaugh said Wednesday that the competition remains wide open.
When asked if McCoy has shown to be the backup, Harbaugh answered, "There's nothing shown there. It's very even. And (I'm) very much looking forward to the games and future practices to determine (it). It's not clear-cut at that position."
Scott Tolzien and McCoy have been sharing second-team repetitions in practice. Rookie B.J. Daniels, a seventh-round pick, also figures into the competition, Harbaugh said. Daniels has also seen action at wide receiver, running back and on special teams.
A year ago, Tolzien won a competition against veteran Josh Johnson to earn the No. 3 job despite having a subpar exhibition season. Tolzien completed just 18 of 34 pass attempts (52.9 percent) for 165 yards with no touchdowns and two interceptions. Meanwhile, Johnson was much better, statistically. He completed 15 of 25 (60 percent) for 219 yards with two touchdowns and no interceptions.
Harbaugh said Tolzien must approach his work as if he's not just battling to win a spot on the 53-man roster but to become a major contributor to a winning team.
"I think he's on that stage," Harbaugh said. "(As a) third-year quarterback, he has to be thinking that way and demonstrating that."