I hate to break it to you Patriots fans, but Tom Brady can’t play forever. The legendary New England quarterback is in his 16th year in the league, and while he hasn’t shown signs of slowing down, at age 39, you have to think he will be looking to hang up those cleats in the next 2-3 years.

With Brady being the undisputed (or as close as you can ever get to undisputed in sports) best quarterback in the league, his eventual retirement will open the door for someone else to take that crown.

Brady represents the end of a very dominant era, where he and Peyton Manning rewrote the record books practically every year. They squared off in some of the most memorable games of the last decade and consistently drew in viewers whenever the two matched up. Manning is already gone and with Brady set to follow in the near future, who exactly will step up to fill the void.

It is kind of hard to say. The iconic 2004 draft class of quarterbacks featuring Eli Manning, Ben Roethlisberger and Philip Rivers likely still have a few more years in them. However, Rivers turned 35 today, Roethlisberger will be 35 in March and Eli Manning turns 36 in January. That group likely won’t be around for a whole lot longer to constitute an era or start an awe-inspiring rivalry. Most of their time in the league will be remembered as part of the legendary Brady-Peyton era.

You next look to Aaron Rodgers, who joined the league in 2005. Rodgers just turned 33 last week, so he might be able to hang around a little longer than the three I just mentioned. However, he might have already started showing signs of slowing down with his rocky start to 2016. I could see Rodgers having a three-year run as the unquestioned top signal-caller. He might be the best-suited to succeed Brady in the short term. Keep in mind that even though this is his 12th NFL season, Rodgers did not start his first three years in the league, so he might have a bit more left in the tank than we think.

After Rodgers, well I’m kind of stuck. Drew Brees is a Hall of Famer, but approaching 38, I’m not expecting him to take over. Carson Palmer is on his way out as well. As will Alex Smith.

There is an interesting crop of three quarterbacks that offer some intrigue. Andrew Luck, Russell Wilson and Cam Newton all bring a lot to the table. All three of them are 28 years old or younger, all three are rather mobile and all three have the ability to take over a football game.

The major knocks against Newton are his ball security and his completion percentage. For his career, Newton sits at around 59 percent through almost 6 seasons. While he may be a huge asset with his legs, he is prone to fumbling and trying to do too much with the ball, often leading to mistakes. Another big red flag is that despite tossing 35 touchdowns in 2015, it is the only season he has thrown more than 25 scores. This year, he has just 14 through 12 games. Those numbers don’t exactly scream elite.

Luck was named the heir apparent to the NFL quarterback throne around his junior year of college. He started with two solid campaigns, followed by an outstanding 2014, only to fall into a weird funk for the last year and a half. 2015 was a lost season for Luck as he only played 7 games and likely played all of them hurt. The big knock against him has to be his lackluster completion percentage, which is only fractionally better than Newton’s. He also has a tendency for interceptions, with 63 picks in 66 career games. Part of that is due to the amount of pressure he faces. Luck is the most sacked quarterback in the league despite missing a game already this year. Luck is actually trending up after the last few weeks we’ve seen him play. Even though he has a poor supporting cast, Luck has failed to live up to Manning-sized expectations laid on him back in 2012.

Then there is Wilson. He already has a Super Bowl ring. Point all you want to a great run game and defense, but that’s a good chunk of why Brady got his first three rings. Of these three, he seems the most poised to take the throne. Wilson has only 39 interceptions in 72 career games. He is closing in on his second consecutive 4,000-yard season and his career completion percentage is around 65 percent. However, when Wilson is off, he is really off. In Seattle’s three losses this year, he has thrown zero touchdowns, three picks and has a yards per attempt average under 6.5. If I had to pick someone long term when it comes to taking up the quarterback mantel, it would be Wilson. He already has that championship background and I could see him getting more.

And he might just have a West Coast rival to deal with as well. There are a number of intriguing young quaterbacks in the league right now in Marcus Mariota, Jameis Winston, Carson Wentz and Dak Prescott. Long term, we might see a really fun rivalry between Prescott and Wentz, both being in the NFC East. However, there is one young quarterback that stands head and shoulders above the rest.

Derek Carr is in the midst of an MVP-caliber season. At only 25 years old, Carr has been lighting up NFL defenses all year long. He launched 32 touchdown passes a year ago, in just his second NFL season and threw for just shy of 4,000 yards. This year though, Carr is set to break that 4,000-yard mark and throw for close to 32 touchdowns again. What is more impressive though is the increased completion percentage and absence of turnovers. The young Raiders quarterback has only thrown five interceptions this year and raised his completion percentage four plus points to a healthy 65.5 percent. This is just one year for Carr, but based on the jump he has made in each of his first two seasons, I am beginning to think that this kid is for real.

I would be remiss not to mention Matt Ryan in this conversation. Ryan is in the midst of a career year at age 31. He is on pace to set career highs in completion percentage, passing touchdowns and yards per attempt as well as set a personal best for fewest interceptions thrown. If Carr is considered an MVP candidate, Ryan certainly has to be in the mix. He currently sits second in passing yards and passer rating, third in touchdowns, fourth in completion percentage and leads the league in yards per attempt. Given that he has a host of offensive weapons and a young offensive line, Ryan is set to play at a high level for the next several years. The tough thing is figuring out if 2016 is an anomaly based on his normal level of play or a sign of things to come. Also, if Brady hangs on for three more years, Ryan will already be 34 himself and running out of time to capture the league’s attention.

The world without Brady is kind of hazy and there is no telling if we will ever see the type of rivalry we saw between he and Manning. The league seems to be running out of elite quarterbacks, but we will have to wait and see who steps up to the plate in the next few years.