The 49ers could get back quarterback Alex Smith from a concussion, but with the way Colin Kaepernick performed in a rout of the Bears on Monday night, it’s uncertain who will get the call from coach Jim Harbaugh.

Regardless, it’s the San Francisco defense that could decide things. If the 49ers can put pressure on Drew Brees and the increasingly dynamic Saints offense — Aldon Smith leads the NFL with 15 sacks — they could control matters. But New Orleans has won three straight and five of six, and Brees could become the third player with 30 TD passes in five seasons.

Green Bay (7-3) at New York Giants (6-4)

The last time they met, New York eliminated a 16-1 Packers team from the playoffs. At Lambeau Field.

The Giants will need to rekindle the overwhelming pass rush that was decisive in that game, plus get Eli Manning back on track. He’s struggled the last two weeks, both losses, and hasn’t played particularly well in a month. A better running game also would help him.

Green Bay, though, has five straight victories and is tied with Chicago atop the NFC North. In his past seven games, Aaron Rodgers has 24 touchdowns, four interceptions and a 117 QB rating. There’s a chance he could get back top receiver Greg Jennings from a torn abdominal muscle, too.

Atlanta (9-1) at Tampa Bay (6-4)

Atlanta lost for the first time two weeks ago, then needed to rally to beat Arizona. The Falcons have won six of the past seven meetings with the Bucs, but those were different Tampa teams. This one is as potent on offense as, well, Atlanta.

Buccaneers rookie Doug Martin already has rushed for 1,000 yards and seven touchdowns.

‘‘Their rookie running back has had some really explosive games,’’ Smith said. ‘‘It will be a challenge for us.’’

But covering Roddy White, Julio Jones and Tony Gonzalez will be a huge challenge for the Bucs.

Baltimore (8-2) at San Diego (4-6)

The Ravens will have star safety Ed Reed as they seek their fourth successive victory and eighth in nine games. His one-game suspension for illegal hits was overturned on appeal and instead he was fined $50,000.

Reed and the Baltimore defense haven’t played close to the level of previous standards, but did have a strong performance in taking charge of the AFC North last week at Pittsburgh.

San Diego, loser of five of its last six, leads the NFL in throwing interceptions (14) as Philip Rivers struggles without much supporting talent compared to previous years.

Pittsburgh (6-4) at Cleveland (2-8)

Plax is back in Pittsburgh.

Unfortunately for the Steelers, the addition of wideout Plaxico Burress, who was without a team all season, doesn’t offset the slew of injuries on offense. Ben Roethlisberger (shoulder, ribs), Antonio Brown (ankle), Jerricho Cotchery (ribs) and Byron Leftwich (ribs) have been sidelined, but Brown could return in Cleveland.

Fortunately for the Steelers, they have a trio of hefty running backs who have come through in Rashard Mendenhall, Jonathan Dwyer and Isaac Redman.

The Browns blew a 13-0 lead in Dallas last Sunday, another sign of their inexperience. They do play hard for coach Pat Shurmur, who is trying to save his job.

Denver (7-3) at Kansas City (1-9)

The Broncos have won five straight and have their sights on running the table, perhaps grabbing home-field advantage for a portion of the AFC playoffs, if not for the whole thing. Peyton Manning needs one victory, something he’s likely to get against the collapsing Chiefs who have dropped seven in a row, to have the second most by a starter in league history. He would move ahead of his current boss, John Elway.

Manning is directing a precise offense, but Denver lost leading rusher Willis McGahee to a right knee injury. The Broncos’ defense is getting superb play from Von Miller, who had three sacks last week for 13 this year.

KC leads the NFL in turnovers with 31 and has a minus-21 differential. Denver’s minus-3 pales in comparison.

Seattle (6-4) at Miami (4-6)

One game after beating his former player at Southern Cal, Jets QB Mark Sanchez, Seahawks coach Pete Carroll goes against one of his Heisman Trophy winners, Reggie Bush. Well, Bush did win the Heisman, but gave it back after he was found guilty of NCAA violations.

Seattle’s defense gets better and more physical each week, something Bush figures to learn Sunday. Bush has totaled 41 yards rushing over the past two games, part of a three-game skid, and even was benched in that span.

Buffalo (4-6) at Indianapolis (6-4)