Three NFL teams (the Broncos, Chiefs and Saints) remain undefeated heading into the sixth week of the 2013 season, while four (the Steelers, Jaguars, Giants and Buccaneers) are still looking for their first win. Here are the storylines we're following this week:

Philadelphia Has a Developing QB Controversy

Raymond James Stadium, Tampa, Fla. — 1 p.m. (ET) on Sunday, Oct. 13

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With starting quarterback Michael Vick likely sidelined with a hamstring injury, Philadelphia (2-3) will presumably start second-year QB Nick Foles against Tampa Bay (0-4). Foles was solid in Philly's win over the pathetic Giants defense last week, and he posted his only win last season over the Buccaneers. A big game from Foles might mean a full-blown quarterback controversy in a city where fans love a sports argument. Tampa coach Greg Schiano has selfish motives for keeping Foles under control: keeping his job. A big loss might mean the end of Schiano's Buccaneers tenure.

Yes, the Lions-Browns Game Is Relevant

FirstEnergy Stadium, Cleveland — 1 p.m. (ET) on Sunday, Oct. 13

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No, you haven't fallen into a DeLorean and been transported to the late 1950s: Cleveland (3-2) and Detroit (3-2) are each tied for the lead in their respective divisions. In 2013, yes. Who cares if it's more a result of early-season scheduling quirks than parity? The game is relevant. Browns QB Brandon Weeden will get yet another chance to impress (or depress) Cleveland fans, while the Lions hope all-world WR Calvin Johnson can return and make his presence felt in the Browns' secondary.

The Broncos Are the Biggest Favorites in Modern NFL History

Sports Authority Field at Mile High, Denver — 4:05 p.m. (ET) on Sunday, Oct. 13

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When undefeated Denver (5-0) faces winless Jacksonville (0-5), the Broncos will be a 28-point favorite—the highest margin since the NFL-AFL merger in 1970. If the line moves any higher, even the Broncos might be tempted to put some cash on the Jags, who will be starting Chad Henne at quarterback for injured starter Blaine Gabbert (not that it would have mattered). Denver QB Peyton Manning could be in street clothes by the second half of this game, if not the second quarter.

The Best Tight End in Football Is in New England

Gillette Stadium, Foxboro, Mass. — 4:25 p.m. (ET) on Sunday, Oct. 13

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While rumors swirl that injured tight end Rob Gronkowski will finally return to the lineup for New England (4-1), Gronk has long since lost his title as the league's best TE. That honor almost certainly belongs to the unstoppable Jimmy Graham of New Orleans (5-0). Graham is a potential MVP candidate, with 593 receiving yards and six touchdown catches already. If he continues on his current pace, he'll set records for the position in both categories, breaking the marks of 1,327 yards and 17 touchdowns held by … Rob Gronkowski.

The Cowboys-Redskins Game Is Still Important

AT&T Stadium, Arlington, Texas — 8:30 p.m. (ET) on Sunday, Oct. 13

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Despite both teams' losing records, there is plenty at stake when Dallas (2-3) hosts Washington (1-3). Each team is still very much in the NFC East "race," but the Redskins must hope that second-year quarterback Robert Griffin III starts to show more progress in his recovery from his knee injury, otherwise they could be forced to consider using Kirk Cousins. The Cowboys have enough talent to be winners, but something always seems to prevent Tony Romo from helping the team realize its potential. Last week, it was his late interception that spoiled his 500-yard passing day and a possible upset of the Broncos.