SANTA CLARA – Go ahead and consider the 49ers’ 34-0 loss to the Denver Broncos as proof.
The 49ers almost certainly will get blown out of any game in the regular season in which. . .
--Colin Kaepernick plays two possessions.
--Frank Gore touches the ball twice.
--Anquan Boldin, Michael Crabtree and Vernon Davis combine for one reception.
--No starters on the defensive line suit up.
--Patrick Willis’ on-field contributions are limited entirely to his pregame speech.
--And their best cornerback, Tramaine Brock, does not play, either.
If all those things happen, the 49ers simply will not be able to compete against any team in the NFL.
Of course, Peyton Manning played two possessions, too. And the Broncos led 10-0 when he exited the game in place of backup Brock Osweiler.
Where things get disconcerting for the 49ers is what happened after that. Osweiler and Zac Dysert, the next two Denver quarterbacks on the depth chart, picked up where Manning left off. They gave the Broncos reliability at quarterback that the 49ers lacked.
The 49ers have good depth on their roster at most positions.
[HARBAUGH: 49ers will not seek outside help at quarterback]
But through two exhibition games, quarterback has not been one of those spots.
In the second half, Blaine Gabbert, Josh Johnson and McLeod Bethel-Thompson were responsible for one turnover apiece. And coach Jim Harbaugh boiled down the competition for the No. 2 job to one thing: Taking care of the football.
Gabbert remains the favorite to be Kaepernick’s backup because nobody else has raised the bar to a level where the 49ers would seriously consider dumping the player who has a fully guaranteed $2 million pay check awaiting him this season – whether he’s on the team or not.
“In terms of a backup quarterback, it’ll be as simple as whoever doesn’t turn the ball over,” Harbaugh said. “They’re turning the ball over. All of them have. There’s nobody to elevate. Whoever doesn’t turn the ball over will be the backup quarterback.”
The bottom line is that the 49ers, like just about any other contending team in the NFL, would experience a significant drop-off if they ever have to call on their backup quarterback.
Backups at other spots will be called upon to help keep the team afloat at the beginning of the season.
All-Pro linebacker NaVorro Bowman is expected to miss at least half of the season due to the knee injury he sustained in the NFC Championship game. Whomever replaces Bowman -- either Michael Wilhoite or rookie Chris Borland -- will have the advantage of playing next to Patrick Willis.
And the 49ers expect the NFL this week to announce discipline for outside linebacker Aldon Smith. Four games? Six games? Eight games? Whatever it might be, the 49ers will piece together a way to compensate for one of the game’s best pass-rushers.
Right guard Alex Boone remains a holdout. Joe Looney played better Sunday against the Broncos than he did the previous week against the Baltimore Ravens.
The 49ers’ defense should still be among the best in the league. But the offense will likely have to be more explosive and score more points this season.
Does it matter that the 49ers got shut out in an exhibition game? Gore and Crabtree played three snaps apiece. Boldin and Davis were on the field for seven plays.
Beginning Sept. 7 at the Dallas Cowboys, the 49ers will feature Kaepernick, Gore, Crabtree, Boldin and Davis in a lot more than just cameo roles.