SEATTLE — One cross-country trip to the Pacific Northwest during the grayest, wettest time of the year is difficult enough.

A slip-up against the Seattle Seahawks on Sunday, and the Atlanta Falcons could be booking a return trip during the playoffs.

Atlanta, the hottest team in the NFC, winner of seven straight and the class of the conference with three weeks left in the regular season, still hasn’t nailed down the NFC South. A poor showing against Seattle could result in a wild-card berth.

The Seahawks, losers of five of seven and coming off a 19-point loss to San Francisco, are still in position to win the worst division in the NFL and earn a home game in the first round of the playoffs.

With New Orleans nipping at Atlanta in the division standings and a Monday night showdown between the two in Atlanta on Dec. 27, a flub by the Falcons could mean another cross-country flight in just a few weeks for a playoff meeting.

Amazing that 11-2 versus 6-7 can have so much meaning.

Maybe that’s why Falcons’ president Rich McKay suggested a change to the playoff seeding structure at the owners meetings this week.

“It really gives us a tremendous challenge to match up with these guys,” Seattle coach Pete Carroll said. “It forces us to play really, really solid football. We will not be able to make mistakes and stay with these guys. They’re just too good at it.”

Atlanta can simplify the situation by taking care of the slumping Seahawks. A win for the Falcons would wrap up a playoff berth and make the matchup with New Orleans likely for the division title and home-field advantage throughout the playoffs.

A stunning loss to Seattle would snap the Falcons’ longest win streak in a dozen years, open the division door for the Saints — barring their own stumble — and bring the real possibility of a return trip to chilly Seattle for a wild-card game.

“We know we have no room to spare,” Atlanta receiver Roddy White said. “We can’t go out there and give up a game because those guys will be right there with us, so we’re just out there trying to win them all and we know we can’t give away any games, especially ones that we’re supposed to win.”

The Falcons are closing out a difficult stretch of three straight road games and four of their last five away from the Georgia Dome.

While Seattle owns just one win over a team with a winning record, Atlanta has made its finest run since 1998 against some of the top teams in the league. In their current seven-game streak, four of the victories have come against winning teams with a combined 33-19 record. And that doesn’t include the Falcons’ overtime win at New Orleans earlier this season.

No wonder Carroll and the rest of the Seahawks were falling over themselves raving about the Falcons this week. In his weekly media conference, Carroll used “challenge” seven times in direct reference to the Falcons.

Ask anyone in the Seahawks locker room about the Falcons and they spoke with the utmost reverence for what Atlanta has accomplished in the three years since coach Mike Smith took over and quarterback Matt Ryan arrived.

Seattle safety Lawyer Milloy brings firsthand perspective, having played for the Falcons from 2006 through the 2008 season, the first year under Smith. He puts Ryan in the same category as Tom Brady, another quarterback Milloy has played alongside.

“He’s a guy who understands defenses, but also understands all he has to do is steer the ship and get the ball into the playmakers’ hands and if he does that he’s still going to be a star,” Milloy said.

Ryan’s favorite target is clearly White, who has already set a career-high with 99 receptions this season and now gets to pick on a Seattle’s 30th-ranked secondary. Michael Turner also could be bound for a big game against Seattle’s regressing defense after reasserting himself last week at Carolina with three rushing touchdowns.

After a slow start, Turner has topped 100 yards rushing in five of his last seven games and scored touchdowns in six of seven.

“We’re really tough to handle right now because I feel like all of our guys are starting to hit their peak and they’re starting to hit their mark,” White said.

While Seattle is clearly overmatched in most areas, they could be a problem for the Falcons thanks to an offense that will be as close to 100 percent as it’s been all season.

Receivers Mike Williams and Ben Obomanu are expected to play after missing last week’s loss to San Francisco with injuries. Williams had a sprained ankle that compounded an already balky left foot strain, while Obomanu couldn’t make it back from a severe cut on his hand from Week 13 against Carolina.

Their returns should instantly help quarterback Matt Hasselbeck, who is coming off the first five-turnover game of his career. Without his top two targets, Hasselbeck was careless with the ball against San Francisco, throwing four interceptions and coughing up a fumble. After five solid games in the middle of the season in which he heeded Carroll’s mantra of protecting the ball, Hasselbeck now has eight interceptions in the last three games.

And Seattle still has major control in how the NFC West will play out, thanks to a season-ending home game against St. Louis.

“Back in March if you told me all it took was three games to get into the playoffs I’d take it,” Milloy said.