RENTON, Wash. — When the Seattle Seahawks prepared two weeks ago to face the 49ers, there was little way to predict the way the fates of the two teams would change by the time they prepared to play each other again this Sunday in Seattle.

The two teams were each 7-4 at that time, the 49ers a slight favorite to beat the Seahawks and send their playoff hopes into an even more uncertain state.

Seattle beat the 49ers 19-3 on Thanksgiving night, however, and then went on to win at Philadelphia last Sunday to improve to 9-4.

The 49ers, meanwhile, suffered their most shocking loss of the Jim Harbaugh era to Oakland to fall to 7-6, and now come to Seattle regarded as a team in danger of a lost season with a coach on the way out the door.

As might be expected, though, the Seahawks weren’t doing much biting on that storyline this week.

“We don’t see this game any different,” said Seattle coach Pete Carroll. “We see the same players, coaches, styles. We remember what’s going on and how they’ve been. They’re very close to being how they need to be at the end of the year and nobody knows how this story is going to be written at this point.”

Seattle, though, was quickly elevated to a 10-point favorite at many Las Vegas sports books, the biggest spread against the 49ers since Harbaugh became coach in 2011.

That spread is based also on the fact that the Seahawks have won three in a row, and six of seven overall, with a defense that is again contending for honors as the best in the NFL

Seattle has allowed just 303 yards in the past two games and 507 in the past three, which according to STATS, Inc. is the fourth-fewest allowed over a three-game span by any NFL team since 2006. That comes against three teams that have a combined record of 26-13.

Much of the reason for the surge is a return to health of the Seattle defense, which now has 10 of its 11 projected starters (all but nose tackle Brandon Mebane, out for the season with a hamstring injury).

“If there’s anything that you should have witnessed here in the last month is that our team speed picked up,” Carroll said. “You can see us playing faster as we’re going. That’s in the continuity and in the communication. That’s in the confidence from being together and being out there. We’re hoping it can happen again one more time.”

It was there when the Seahawks beat the 49ers, holding them to 164 yards and with Richard Sherman picking off Colin Kaepernick twice, plays that defined Seattle’s dominance in the game.

Kaepernick has thrown seven of his 21 career interceptions against Seattle and is 0-3 in three starts at CenturyLink Field, including the NFC Championship Game last January.

Seattle, though, remains in a must-win situation, standing still a game behind Arizona in the NFC West, which has Carroll predictably wary of assuming anything about the two paths the two teams appear on.

“It’s so fleeting, the past couple weeks,” Carroll said. “This week’s a whole, new story and we’ve got to find it again.”