If a backup quarterback's job is to seamlessly replace the starter, then Gus Frerotte has finally fulfilled his duties. He's playing every bit as erratically as Tarvaris Jackson.

Sunday at Jacksonville, Frerotte held the ball when he should have thrown it, tossed an inexcusable interception, looked antsy in the pocket, and proved unproductive against another defense primed to stop the run.

Even as they look prepared to take over first place in the NFC North -- a prize that comes with a set of steak knives -- the Vikings are establishing that they may have the worst quarterback situation in the NFL. (This exempts Detroit from the NFL. The Lions should hereafter be considered an at-large MAC team. I say this at the risk of getting sued by the MAC.)

The Vikings' quarterback depth chart is as follow:

• The 37-year-old Frerotte.

You've heard of NFL player hitting the rookie wall? Frerotte is hitting the Geritol Wall. A month ago, he was moving like Drew Brees. Now he's moving like Drew Carey.

• The 25-year-old Jackson.

He destroyed the organization's faith in him in only two games at the start of the season, throwing a horrific interception at the end of the Packers game and failing to beat a Colts' defense so injury-ravaged it was trying to recruit Gino Marchetti out of retirement.

• The 23-year-old John David Booty.

I'm rooting against him ever playing, because Chris Berman would be so gleeful about the pun possibilities attached to Booty's name that Berman might have a heart attack.

On second thought, I now have a reason to root for John David Booty.

If Frerotte can remain ambulatory and sneak the Vikings into the playoffs, the Vikings can pretend this all went according to plan. But, really, who's in worse shape at the position, other than teams who have lost a starter to injury?

The Raiders stink, but they at least they're basing their hopes on a talented first-round draft pick, JaMarcus Russell. The Bengals stink, but that's largely because Carson Palmer is hurt. The Rams stink, but quarterback is not their problem. The Browns stink, but Brady Quinn looks promising.

The Chiefs stink, but former Vikings draft choice Tyler Thigpen is proving he's the best quarterback the Vikings have had since Daunte Culpepper left, even if they never let him on the field. Only the 49ers can contend with the Vikings in terms of quarterback haplessness. It's always good to draw comparisons with a team whose coach removes his pants at halftime.

If the Vikings had ever pursued a playoff-caliber quarterback with same zeal with which they pursued Jared Allen, Bernard Berrian and Brad Childress himself, this team would be debating whether to rest its starters for the playoffs. Instead, Childress is saddled with this choice: Faltering Frerotte and Inaction Jackson.

The New York Giants running backs have nicknamed themselves Earth, Wind and Fire. The Vikings quarterbacks are more like Pestilence & Famine. The Vikes rank 26th in passing yards per game despite the arrival of Berrian and the insistence of opposing defenses on stopping the Vikings running game.

This is not the fault of Jackson and Frerotte. Both of them give you all they've got. It's the fault of the Vikings' amorphous front office.

Jackson is a poor fit for an ambitious, veteran team, and Frerotte had to be talked out of retirement. He did the job he was expected to do -- he played well in relief for a few weeks. This team never was supposed to rely on him to start 14 games.

Problems always start at the top. Vikings owner Zygi Wilf has invested lots of emotion and cash in the team, but he never hired a true general manager, someone who would insist on the obvious: If you want to make a serious run at a championship, you need a real starting quarterback.

Almost four years into the Wilf Era, nobody in charge has done anything to improve the most important position on the team.

Jim Souhan can be heard Sundays from 10 a.m.-noon on AM-1500 KSTP. • jsouhan@startribune.com