The moment Garrett Hartley's foot drove through the ball, the Louisiana Superdome crowd erupted and Saints owner Tom Benson raised his arms in triumph.

The presumption was that these Saints, in this magical season, were going to pull out another win in the clutch.

Not so fast.

Hartley's 37-yarder hooked to the left, and those who'd allowed themselves to celebrate prematurely were sent home soon after in stunned silence.

Carnell Williams rushed for 129 yards and a score, and Connor Barth kicked a 47-yard field goal in overtime, lifting Tampa Bay to a 20-17 upset on Sunday that, for the time being, prevented New Orleans from securing home field throughout the NFC playoffs.

Even in what will go down as the best regular season in Saints history, a franchise long known more for its stumbles than success found a way to make history with a loss. According to STATS LLC, the result marked the first time a 13-win team lost to a team that came in with only two victories.

"It's hard to explain," Saints quarterback Drew Brees said. "We started off fast, then after that there was a big lull."

Kind of like their season.

New Orleans (13-2) won nine of its first 11 games by double digits. After a 38-17 win over New England, the Saints appeared better situated than ever to make the franchise's first run to the Super Bowl.

Since then, the Saints have pulled out a pair of three-point wins over non-playoff teams and have lost two straight _ both at home _ starting with a 24-17 setback to Dallas.

If Minnesota wins its final two games, starting Monday night in Chicago, the Saints will have to win in Carolina next Sunday to secure the franchise's first No. 1 playoff seeding.

"The fact is we need to play better," Brees said. "I don't feel like we've played our best football in a while and there's definitely some things that need to be corrected.

"You always find out more about a team when you start facing adversity. This is just yet another one of those situations that I feel we have the right character, the right type of leadership to bounce back from and help us become stronger going into the playoffs."

New Orleans was favored by more than two touchdowns over the Buccaneers (3-12).

New Orleans sped out to a 17-0 lead with its first three possessions, but the Bucs, who have refused to quit on the season, cut it to 17-3 on Barth's 34-yard field goal as time expired in the first half.

"We went back in the locker room and I tried to settle the guys down," first-year Tampa Bay coach Raheem Morris said. "They believe in me and I believe in them. ... I know this team is getting better. I could see it every week, even when we were losing."