The Super Bowl champion Baltimore Ravens are symptomatic of what is happening in the NFL. Change is happening everywhere, from the way offenses have employed the spread and option read to the rule changes that will penalize an offensive player for using his helmet to deliver a blow.
After getting a fortuitous misplay in Denver that kept them on the road to the Super Bowl, the Ravens lost three All-Pro players from their roster, including their spiritual leader, middle linebacker Ray Lewis, and larcenous big-play safety Ed Reed. They also lost several of their complementary players on defense, most notably linebackers Paul Kruger and Dannell Ellerbe.
But don't discount the Ravens. They've kept the core of their roster intact with their key players, including Super Bowl MVP quarterback Joe Flacco, running back Ray Rice, defensive tackle Haloti Ngata and defensive end/linebacker Terrell Suggs. And they added former Broncos defensive end Elvis Dumervil, who will have a bigger impact on the defense than any of the players they lost.
Is that enough to repeat? Probably not in this day and age, when the last repeat Super Bowl champion was the New England Patriots in 2004-05.
Here is a look at some of the key story lines for the 2013 season:
Patsies or Patriots? What is Tom Brady going to do? Speedy and dependable receiver Wes Welker is gone, tight end Rob Gronkowski is hurt and tight end Aaron Hernandez is in jail. That means Brady's top returning target is Julian Edelman, who had 21 catches last season. Maybe that 40-9 preseason loss in Detroit wasn't a mirage after all.
Chuck the tuck. Speaking of Brady, NFL owners did away with the controversial tuck rule in the offseason, hoping to eliminate the gray area of determining just when a quarterback begins his throwing motion on a pass. The rule change is not soothing any of the hard feelings that still exist in Oakland.
Can anyone stop Adrian Peterson? Probably not; not after the Minnesota Vikings running back rushed for 2,097 yards in 2012, just the sixth back in history to eclipse 2,000 yards rushing. But the league is trying to eliminate one of his favorite tactics by now penalizing running backs who use their helmets to deliver a forcible blow. Defensive players around the league, tired of being targeted for helmet blows, are ecstatic.
Luck or talent? Andrew Luck passed for more yards (4,374) than any rookie quarterback in NFL history in leading the Indianapolis Colts to 11 wins and a playoff spot. But can he and last year's other hotshot rookie quarterbacks -- Robert Griffin III and Russell Wilson -- do it a second time around? Each led their respective teams to the playoffs last season, but, as Cam Newton found out last year, it's gets a little more difficult as a sophomore.
Dalton's gang. Andy Dalton has done something in two seasons with the Bengals that icons Ken Anderson and Boomer Esiason never did in Cincinnati -- take the team to the playoffs in his first two seasons. Don't look now, but the Bengals have made the postseason three of the past four seasons. The addition of tight end Tyler Eifert, their No. 1 pick, makes Dalton even better, especially with wide receiver A.J. Green on the outside. Green has more catches (162) in his first two seasons than any player in NFL history.
New coaches. Former Steelers offensive coordinator Bruce Arians pulled off a rare coup in 2012, being named coach of the year without ever officially being the head coach. But he is now, parlaying what he was able to do with the Colts when he filled in for ailing Chuck Pagano into the head coaching position with the Arizona Cardinals. Arians is one of eight new head coaches in 2013, two of whom came from the college ranks -- Chip Kelly (Eagles) and Doug Marrone (Bills). But can Arians get out of Carson Palmer what he was able to do with Ben Roethlisberger and Andrew Luck?
Red for Reid. The Kansas City Chiefs were the first team to have six Pro Bowl players and fewer than six victories in the same season in 2012, according to Elias Sports Bureau, and they're hoping to change that with the hiring of Andy Reid as head coach. Reid took the Eagles to five NFC title games and one Super Bowl and had winning records in nine of his 15 seasons in Philadelphia. With a roster that has talent at every level, the Chiefs are a good bet for one of those dramatic turnarounds.
Payton's place. Sean Payton is back as head coach in New Orleans after a one-season ban for his role in Bountygate. And that is good news for the Saints offense, which doesn't need a lot of help with quarterback Drew Brees. Payton, though, needs to find a way to fix the defense, which gave up 7,042 yards in 2012, most in league history.
Bucking the Broncos. Denver thought it was just a couple seconds from an appearance in the AFC title game last season until the Broncos blew a deep coverage against the Ravens and, well, you know the rest. Peyton Manning is back for another season and should even be better in what was an MVP-caliber year in 2012. The addition of Welker will make him even more dangerous in the middle of the field. But losing outside linebacker Von Miller for six games because of a league suspension will hurt.
Tebowmania gone. Tim Tebow is no longer with the New York Jets, which means the media circus that enveloped his every move should be gone, too. But that doesn't mean there isn't any conflict or consternation with the Jets. Rookie Geno Smith of West Virginia has been involved in a quarterback battle with incumbent Mark Sanchez in training camp, but that was settled when Sanchez got thrown into a preseason game behind a second-team offensive line and promptly came away with a shoulder injury. Keep in mind this is the same team that is just three years removed from back-to-back appearances in the AFC championship game.
Gerry Dulac: email@example.com and Twitter: @gerrydulac.