PITTSBURGH – When Teddy Bridgewater injured his knee last August, Rick Spielman made a shockingly ambitious move, trading for Sam Bradford. He believed his team was built to win, making Bradford worth a high price.

Although injuries ruined the 2016 season, Spielman was right to gamble on Bradford, who has completed a stunning 72.3 percent of his passes as a Viking.

Sunday, Bradford tested his sore left knee on the soft turf of Heinz Field, then the team made him inactive for the game. Case Keenum replaced him and performed like a quarterback who is lucky to be a backup in the NFL. The Vikings lost to the Steelers 26-9, while managing 167 passing yards despite playing from behind the entire game.

Spielman invested heavily in the starting quarterback position, and white-knuckled his nickels when looking for an understudy. Given that the starter has had two surgeries on the same knee and hasn't started 16 games in a season since 2012, Spielman should have done more than settle. He should have again behaved ambitiously and acquired the best quarterback available to him: Colin Kaepernick.

The Vikings were doomed with Keenum in the lineup. Kaepernick would have given them a puncher's chance.

Last year, Keenum threw nine touchdowns and 11 interceptions before being benched. Last year, Kaepernick threw 16 touchdowns and four interceptions. Kaepernick is bigger, stronger, faster, possesses a better arm and has been a starting quarterback in the Super Bowl, where he came within one pass of winning.

The NFL has conspiratorially blackballed Kaepernick for kneeling during the national anthem to protest the unjustified shootings of black Americans by police.

Some owners don't want him on their team, wrongly conflating a peaceful protest with an attack on our country or our soldiers. Some owners, general managers and coaches don't want the headache of Kaepernick's presence and news conferences.

The Vikings discovered Sunday what it costs to take a stand: the chance to win one NFL game or maybe more, which could wind up being the difference between making the playoffs and not, or earning home-field advantage or not.

Kaepernick and quarterback-needy NFL teams are playing a form of social-justice chicken. He's willing to miss games and paychecks to make a point. Will NFL teams desperate for quarterbacks self-sabotage seasons to make theirs?

What we've learned in just two weeks of real games is that there are not nearly enough competent quarterbacks in the league. Kaepernick would improve most, if not all, NFL teams as a starter or backup.

Given that Bradford is not certain to return this week, the choice of Keenum over Kaepernick could continue to cost the Vikings. During a whiny news conference during which he seemed dumbfounded why anyone would ask about an injured starting quarterback, Vikings coach Mike Zimmer insisted "Sam will be fine," then suggested Bradford could miss another week … or six.

"I'm not going to discuss it with you," Zimmer said. "Sam's going to be OK. Maybe the next week, maybe six weeks from now, he's going to be OK."

If Keenum plays a half-dozen games, he could ruin this season as surely as the offensive line ruined last season.

When asked Friday whether Bradford would play against the Steelers, Zimmer said, "I anticipate that he will, yes." We know not to listen to him anymore.

After the game, Bradford was wearing shorts and a T-shirt and shaking hands with his teammates. Players praised Keenum — Dalvin Cook repeatedly mentioning the "energy" Keenum brings to the huddle — and Keenum vowed to be ready if needed.

"He fought his tail off," tight end Kyle Rudolph said.

"I was prepared and ready to go," Keenum said.

These are the nice things teammates say about mediocre players, and the nice things mediocre players say about themselves.

There is no comparison between Keenum and Kaepernick. The Vikings and other teams decided that they prefer comfortable losses to uneasy victories. Sunday's loss was about as comfortably numbing as they get.

Jim Souhan's podcast can be heard at MNSPN.com. On Twitter: @SouhanStrib. • jsouhan@startribune.com