When Colin Kaepernick tucks the ball underneath his arm and runs for the end zone, 49ers fans may want to hold their breath.
After two preseason games, one thing is obvious: If the 49ers are to win the Super Bowl, Kaepernick can't get hurt.
There is no safety net, meaning there is no reliable backup quarterback if Kaepernick is injured this season.
The 49ers' concern already is obvious, with coach Jim Harbaugh benching Kaepernick after three offensive plays Friday and explaining to reporters in Kansas City that he "didn't want anything freakish to happen" to his starter.
The 49ers acquired Colt McCoy to back up Kaepernick, but after McCoy completed 6 of 13 passes for 76 yards with two interceptions in the first two preseason games, we understand why the Browns kicked him to the curb for a rookie last season.
But with a $1.5 million contract more than Kaepernick's salary more is expected from McCoy.
Last season's No. 3 quarterback, Scott Tol- zien, made the 2012 roster despite being outplayed by Josh Johnson. Now Tolzien is being outplayed by rookie B.J. Daniels, a seventh-round pick.
Daniels played the best of the backups in Friday's 15-13 win at Kansas City, throwing the team's first touchdown pass of the preseason and completing 6 of 9 passes for 72 yards.
But it doesn't matter if McCoy, Tolzien or Daniels is the 49ers' backup quarterback.
None can replace Kaepernick.
What to watch
Baseball, A's vs. Mariners, 7:05 p.m., CSNCA: Oakland continues its battle for the American League West title.
Who should be the 49ers' backup quarterback?
Vote above or leave your comments in the comments field; or, go to www.sacbee.com/sports
Did Angel Pagan's injury doom the Giants' season?
Yes, they're better with him: 69%
No, his absence doesn't matter: 31%
Total votes: 124
Call The Bee's Victor Contreras, (916) 326-5527. Follow him on Twitter @SacBeeVictor.