The Houston Texans have a chance to climb into AFC South contention against the Indianapolis Colts, whose quarterback Andrew Luck is still less than 100 per cent.

Luck missed last weekend's 16-13 win over the Jacksonville Jaguars with a shoulder injury and is questionable again for Thursday. His backup, 40-year-old Matt Hasselbeck, played well against the Jaguars but does not expect to play this week because of an illness.

That means newly signed Josh Johnson could get the start in Houston. It would be a nightmare scenario for the Colts against a Texans defense that can get after the quarterback. Johnson, a fifth-round pick of the Tampa Bay Buccaneers in 2008, has five career starts with 1,042 passing yards, five touchdowns and 10 interceptions. 

For all of their issues at quarterback, the Texans defense is solid with defensive end J.J. Watt leading the way. Luck said he is preparing to start but definitely will not be at his peak physical level. This is a window of opportunity the Texans must seize.

Houston boast the NFL's seventh-ranked offense and getting some productivity from running back Arian Foster will help. But the Texans have hurt themselves with a minus-six turnover ratio. If they take care of the ball, the Texans can expose a vulnerable Colts defense and outscore an offense that is hurting. 

There are six undefeated teams remaining and three of them have key matchups on Sunday.

Patriots (3-0) at Cowboys (2-2), 4:25 p.m. ET

Had Tom Brady's suspension stuck, the Patriots quarterback would not be playing in this game, and had the 10-game suspension handed to Cowboys defensive end Greg Hardy remained, he would be out as well. But Brady's ban was lifted and Hardy's suspension was reduced to four games, so both will be on the field at AT&T Stadium. Hardy will be playing in his first game in almost 14 months.

New England's offense has been unstoppable so far, averaging a league-best 40 points per game. Dallas should be thankful to get Hardy back because they will need him to bolster a pass rush that has just six sacks on the season. That said, it is hard to imagine Brandon Weeden, still at quarterback in place of injured starter Tony Romo, getting the best of Brady. The Cowboys also lost a key weapon when third-down back Lance Dunbar was lost for the season with a knee injury against the New Orleans Saints.

Seahawks (2-2) at Bengals (4-0), 1 p.m. ET

Bengals quarterback Andy Dalton is on fire through four weeks, leading the AFC with a 123.0 passer rating, but the red-hot Cincinnati offense will be tested by a Seahawks defense that got its leader back in safety Kam Chancellor, who forced a game-saving fumble in Monday's win over the Detroit Lions.

After allowing 61 points and three touchdown passes in losses to the Rams and Packers while Chancellor was holding out, Seattle has surrendered just 10 points since and no touchdown passes since his return. The Seahawks offense still has not gotten on track, especially a dormant ground game that is not the same without Marshawn Lynch.

The Bengals are fourth in scoring and second in total offense, but Dalton will have to spread the ball around because Seattle's 'Legion of Boom' secondary will try to shut down receiver A.J. Green, who has 25 receptions for 417 yards and three touchdowns through four games. Things will be easier for Cincinnati if they get their own rushing game going by pounding the ball with Giovani Bernard and Jeremy Hill.

Rams (2-2) at Packers (4-0), 1 p.m. ET

The Rams and Packers are tied for second in the NFL with 17 sacks apiece. The Rams have one of the NFL's most formidable defensive fronts but have lost leading tackler Alec Ogletree to an ankle injury. The Packers have been spreading the wealth with linebackers Clay Matthews and Nick Perry recording three sacks apiece and outside linebacker Julius Peppers leading the team with 3.5 sacks.

The Packers exorcized some demons last week by finally shutting down 49ers quarterback Colin Kaepernick for the first time in four tries.

They face a much simpler offense this week. Although Rams running back Todd Gurley had his breakout game last week in an upset of the Cardinals, the Rams still rank dead last in total offense. If they want to pull off a second straight road upset, they will have to somehow rattle the unflappable Aaron Rodgers.

Green Bay's quarterback has been nearly perfect at Lambeau Field. Rodgers has not thrown an interception there since 2012, a streak that spans 19 games with 580 pass attempts and 48 touchdown passes. The Rams have picked off three passes in four games, cornerback Janoris Jenkins intercepting Carson Palmer in the end zone last Sunday.