Baseball is set to undergo a major change in 2013, as the Houston Astros, members of the National League for 51 seasons, will move to the American League, creating two 15-team leagues and mandating daily interleague play.

Yet, when you think about the 2013 Astros, the first thing to come to your mind is probably not the league switch it's more likely how they're completely rebuilding and are sure to sport a terrible on-field product. (Don't worry: we'll further address the impact of the Astros' AL move in an upcoming column.)

Dynasty League Draft

Last month, a number of ESPN Fantasy analysts conducted a dynasty league draft, incorporating some of the same principles seen in this set of keeper league rankings. Click here for the full draft results.

The Astros' total teardown has been the subject of much chatter the past calendar year, and in every way it parallels, in fantasy, a keeper/dynasty league owner in a rebuilding phase. And in many ways, what the Astros are doing lends credibility to such a fantasy strategy. Consider that, in a calendar year, the Astros went from the No. 27 (2012) to the No. 4 (2013) organization in Keith Law's farm system rankings thanks to an influx of talent including draft picks Carlos Correa and Lance McCullers Jr. and trade acquisitions Jarred Cosart and Robbie Grossman.

That's not to say that the Astros' long-range plan is working, rather that it seems to be working, because we won't know for sure whether many of their prospects will pan out until several years from now. That is the risk for them -- and the risk for a keeper-league rebuilder.

Granted, in fantasy, we'd all prefer to be our league's Alex Anthopoulos -- referring to the Toronto Blue Jays general manager -- getting the green light to spend, spend, spend in our quest for a 2013 title. In every keeper league there'll always be an Anthopoulos but there'll also always be a Jeff Luhnow -- he's the Houston Astros general manager, for those who didn't know.

This column is for those Luhnows, those keeper-league owners who need to be as mindful of 2014, 2015, 2016 and beyond as 2013, those tear-it-down strategists or simply those who want to infuse some youth into an aging roster.

These are my annual Top 250 Keeper Rankings, a "price guide" of sorts for keeper or dynasty leagues, whether previously existing or just starting from scratch. In many ways, they'd be the fantasy equivalent of Luhnow's personal cheat sheet.

The rankings formula

You know the drill: One cannot compose a set of keeper/dynasty league rankings that's one-size-fits-all. (On an aside, I therefore suppose it's fitting that I provide our keeper ranks; in terms of hat sizes, it's one-size-fits-all-except-me.) The reason is that few such leagues are identical in structure. Consider the variables:

• Player pricing: Do you draft or auction players, and do you keep players in the round they are picked, the auction price you paid, or are prices irrelevant?

• Number of keepers: Can you keep 1, 3, 10 or perhaps your entire roster, and must teams retain the same number of players?

• Length of contract: Is there a limitation on number of seasons you can keep a player, and is there annual price inflation?

• Farm teams: Does your league have them, and are these players able to be freely retained or held over at low cost from year to year?

• Competitive state: Are you an Anthopolous, Luhnow or somewhere in between -- say, Chris Antonelli, the general manager of the Cleveland Indians?

It's up to you to do your homework assessing each of these valuation factors. For instance, a $1 Wil Myers might be a slam-dunk keeper in your league over a $31 Matt Holliday, despite the fact that Holliday ranks 10 spots higher in the list below and is the only one of the two guaranteed an Opening Day roster spot.

This is the player valuation formula I use:

• 2013 performance: 25 percent.

• 2014 performance: 25 percent.

• 2015 performance: 25 percent.

• 2016 performance and beyond: 25 percent.

My rationale for weighting 2013 equally to 2016 and beyond is simple: We already provide rankings, projections and profiles for approximately 1,000 players that were designed to help your title quest this year. While I might weight 2013 more heavily in a keeper league drafting fresh -- I always prefer to win sooner than later -- this page is meant to serve fantasy owners projecting players over several seasons. If your goal is to win now -- kudos to you, Anthopolous -- our redraft tools are excellent for your needs.

Tristan's top 250 keeper rankings

Note: Position eligibility is determined based upon a minimum of 20 games, otherwise the position the player appeared at most in 2012. Players' listed ages are as of April 1, 2013. Players' rankings in past keeper lists are also provided: "Pre" are rankings from that year's preseason, while "Mid" are rankings from midseason of the year in question.

On pitching in general

As always, I recommend a keeper-league owner build his or her roster around hitting first and second, taking a more conservative approach to constructing a pitching staff. It is for that reason that only five pitchers -- all starters -- placed among my top 25, and only 27 in my top 100.

Clayton Kershaw is one of the top young pitchers in the game today, but be careful when trying to build a keeper league team around him. Mark J. Rebilas/US Presswire

Only one true closer, Craig Kimbrel, cracked my top 100. (Closer-turned-starter Aroldis Chapman was seven spots behind Kimbrel, and to note, he'd rank approximately the same even if he returns to the closer role.)

Addressing the closers first, the position's volatility in 2012 alone serves evidence why it's a flimsy strategy to build around them in a keeper league. Consider that, in my 2012 preseason Keeper Top 250, Drew Storen was the No. 2 closer at 77th overall, John Axford was the No. 3 closer at 102nd overall, Jordan Walden was the No. 5 closer at No. 109 overall and Brian Wilson was the No. 6 closer at No. 115th overall. Every one of them suffered a significant drop in keeper stock, and Walden and Wilson didn't even make this year's cut.

Ultimately, all it takes is one managerial decision to vault a closer 100 spots or more in this kind of rankings set, and Storen's example might be best: As the ball dropped on New Year's, he might have ranked as high as 137th on this list. Then Rafael Soriano signed a two-year deal with Storen's Washington Nationals, and Soriano is the one you'll find at No. 137.

As for the starters, while I'd argue that in today's increasingly pitching-rich game, ace starters have greater keeper-league value, let's not forget that the career shelf life of such a pitcher can be short. Using the 2012 top 250 as example yet again, Roy Halladay (No. 4 starter, No. 22 player overall), Tim Lincecum (Nos. 9 and 40) and Jon Lester (Nos. 11 and 46) have long-term projections considerably lower today than they did at the time that column was published.

On Bryce Harper

Harper

There is no greater keeper-league debate entering 2013 than the value of Bryce Harper. The No. 3 selection in our January dynasty mock draft, Harper makes as compelling a case for a No. 1 ranking in this list as he has enough risk to place as low as 15th. I'm on record as being one of the more conservative regarding Harper's 2013 expectations -- his young age (he's 20) makes his chances of an adjustment period non-zero, and I'd argue by a decent chunk -- but there are many who are supremely confident in his chances at a top-10 overall season.

This was my Harper summation during our fantasy summit: "I'm somewhat cautious about his 2013, feeling that applying Mike Trout's age-20 breakthrough is dangerous to directly parallel, but if you asked me today to lock in my 2014 overall top 10, Harper would unquestionably be a part of it."

To help you make adjustments to your own keeper rankings, if you believe that Harper is a top-10 overall player for 2013, then he'd be the No. 2 name on the above list. If you believe he is a top-25 overall player, then he'd be third or fourth (depending upon how far into that top 25). I ranked Harper 63rd for 2013, and that's the thinking behind his No. 7 rank in the list above.

Miscellaneous thoughts

Matt Wieters' potential to stay at catcher for many years helps his keeper-league value. Tom Szczerbowski/US Presswire

• Matt Wieters (38th overall) versus Carlos Santana (47th) was one of my most difficult player-versus-player debates within a single position, and is one of the more important keeper decisions to make. Frankly, the deciding factor was that I'm confident in Wieters' ability to spend his entire career behind the plate; I have enough questions about Santana's defense to wonder whether he'll be a first baseman or a designated hitter by 2016.

• Third base is a position extremely rich in terms of potential keepers, and is responsible for 12 of my top 100, including 10 within my top 56 overall. Heck, I wouldn't be opposed to retaining Todd Frazier (115th overall) or Pedro Alvarez (124th), if the league afforded me enough spots. As the vast majority of the league's third basemen are either in or approaching their primes, and there are so many worth your selection, your strategy at this position is critical.

• Everyone's talking about Wil Myers, Jurickson Profar and even starting pitchers like Shelby Miller and Dylan Bundy as the prospects/2013 rookies to get now in a keeper league, but the player whose projected price-versus-expected return, both this and in future seasons, is most attractive to me is Oscar Taveras (107th overall). All it'd take is an injury to either Matt Holliday or Carlos Beltran plus a hot start by Taveras in Triple-A for him to reach St. Louis, and with his plate coverage and power/speed combination, he could be an instant five-category star.

Players who juuuuuust missed

These are not officially my Nos. 251-255 players, nor are they in any particular order. These are merely five players who I had on my initial candidates list but unfortunately were last-minute scratches.

Mike Zunino, Seattle Mariners: The No. 3 overall pick in the 2012 amateur draft, Zunino might have the greatest upside potential of any player excluded from my list. Based on his bat alone he could probably play now in the majors, and since the Mariners aren't exactly rich in catching talent -- defensively speaking, specifically -- there's a chance we might see him this summer. Watch him closely early in the year.

Devin Mesoraco, Cincinnati Reds: Whether your league uses one or two catchers has a bearing on whether he belongs in your top 250, as he was my No. 20 catcher if we went by position. The reason Mesoraco didn't make the cut is that, while his plate discipline remained constant at the big-league level, his bat fell well short of expectations, and injuries were a problem for him in 2012.

Drew Stubbs, Cleveland Indians: I'm simply not a fan, something I've made clear for a few seasons. But in Stubbs' defense, he's a power/speed type entering his age-28 season, and if he gets the at-bats, he'd probably belong in the back end. I simply see the Michael Bourn signing adversely affecting Stubbs the most, and he's the last player I removed from the top 250 following that move.

Kolten Wong, St. Louis Cardinals: He was in my 2012 midseason top 250, ranked 224th, he had .287/.348/.405 rates at Double-A Springfield, and he has a shot at some second-base time in St. Louis this summer. But I look at Wong's profile and wonder whether he'll contribute enough homers and/or steals to consistently warrant mixed-league consideration from 2013-15.

Jonathan Singleton, Houston Astros: Fitting to conclude with an Astros prospect, isn't it? Singleton should see time in Houston later this summer, and he's a patient type who might not need as long to adjust as the average prospect. However, he's set to miss the first 50 games of 2013 following a second violation of the minors' drug policy, and he has a steep platoon split -- more than 200 points lower against lefties than righties.