49ers' Joe Staley might play Sunday

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It appears Colin Kaepernick's blindside might be in a Pro Bowler's capable hands Sunday against the Seahawks, after all.

In a bit of a surprise, 49ers left tackle Joe Staley practiced Thursday and showed no obvious signs of being hampered by the sprained MCL he sustained in a win over the Rams four days earlier. During the first 15 minutes of practice, which are open to the media, Staley appeared to have no issues bending his right knee or moving laterally during individual pass-blocking drills.

On Sunday, Staley, who was limited in Thursday's session, exited early in the first quarter and was ruled out of the game before he reached the locker room. After he failed to practice Wednesday, it was widely assumed he would be sidelined for the game against Seattle.

Staley's injury is clearly far less severe than the sprained MCL sustained by All-Pro left guard Mike Iupati on Nov. 10 at New Orleans. Iupati has missed the past two games and didn't practice Thursday.

Staley's return would be a huge boost against the Seahawks, whose top-ranked defense features a deep and effective defensive line. If Staley and Iupati were unable to play against Seattle, second-year guard Joe Looney would make his first NFL start.

"They've got a stacked defensive front," said guard Adam Snyder, who has subbed for Iupati the past two weeks. "Their linebackers are fast. And we know how the safeties play. They present a challenge to us."

Joe Staley tries to quiet the crowd when the 49ers are in the red zone in the second quarter. The San Francisco 49ers played the Carolina Panthers at Candelstick Park in San Francisco, Calif., on Sunday, November 10, 2013. less Joe Staley tries to quiet the crowd when the 49ers are in the red zone in the second quarter. The San Francisco 49ers played the Carolina Panthers at Candelstick Park in San Francisco, Calif., on Sunday, ... more Photo: Carlos Avila Gonzalez, The Chronicle Photo: Carlos Avila Gonzalez, The Chronicle Image 1 of / 1 Caption Close 49ers' Joe Staley might play Sunday 1 / 1 Back to Gallery

Some of the NFC's top teams - the Saints (9-3), Panthers (9-3) and 49ers (8-4) - have failed to meet that challenge this season.

Seattle sports a 3-0 record against those teams thanks, in part, to a defense that has allowed 5.7 points and 216 yards in those games. How has Seattle shut down such a formidable trio?

"Because we're the best," All-Pro safety Earl Thomas said, jokingly, to the Seattle media. "Nah. We prepare well - our preparation and the way we practice - all of that translates to the game. That's why you see us with those great performances."

Those performances have featured a seemingly bottomless well of defensive linemen. The Seahawks have seven linemen who have played at least 370 snaps this season (the 49ers, in contrast, have two) and have players such as Cliff Avril (28 sacks since 2011) and Michael Bennett (15.5 sacks since 2012) coming off the bench.

Their secondary features Thomas, a defensive MVP candidate, safety Kam Chancellor, a Pro Bowler in 2011, and All-Pro cornerback Richard Sherman, a noted 49ers nemesis.

Niners safety Donte Whitner is busy studying Seattle's offense this week, but he has taken note of the Seahawks' defense this season. Whitner admires its physical style, which reminds him of that of the 49ers'. San Francisco's defense ranks fifth in the NFL and has allowed the fewest points per game at home (13.6) since 2011.

"You don't see guys out there diving around and falling around, or scared to make contact, or scared to do certain things," Whitner said. Things "that players see when we sit in the meeting room. We have respect for them, but we still want to beat them."

Staley's return would increase the 49ers' chances of doing so. They lost 29-3 in Seattle in Week 2. In addition to the Seahawks, the 49ers have lost to the Colts, Panthers and Saints, all of whom would be in the playoffs if the season ended this week. The 49ers' eight victories have come against teams that wouldn't reach the postseason.

Whitner, however, dismissed the suggestion that the defending NFC champions need a win over Seattle (11-1) to erase doubts about their ability.

"We really believe that we're the mighty 49ers and they believe that they're the mighty Seahawks," Whitner said. "So we'll see who comes out on top. We're very confident. They're very confident ... It's going to be a good game on Sunday."