The Dynasty 250: Top keepers for 2017 and beyond

— -- What a time to be young.

As we all digest the first half of the 2016 baseball season during which a 40-year-old  David Ortiz continues to set new standards for older players, the truth is that baseball has only shifted further toward a youth movement. It's the kids who are generating most of the headlines these days.

Among the first half's "youthful" feats:

• The Nos. 3 ( Mike Trout), 4 ( Mookie Betts), 10 ( Wil Myers), 13 ( Jose Fernandez), 14 ( Xander Bogaerts), 15 ( Jonathan Villar) and 19 ( Kris Bryant) names on the Player Rater haven't yet celebrated their 26th birthdays.
• Trevor Story, a 23-year-old who finished the first half 59th on the Player Rater, tied a National League rookie record with 21 home runs before the All-Star break.
• The American League's All-Star starting infield -- Eric Hosmer (age 26), Jose Altuve (26), Manny Machado (24) and Bogaerts (23) -- is younger than any that has appeared in any of the past 86 such contests.
• The average age of the current top 100 on the Player Rater is 28.4, lower than it has been in any of the previous seven seasons.
• A whopping 140 players have made their major league debuts this season, for a seasonal pace of 256. If that holds, this year would shatter the previous record for most debuts, 254, which was just set last season.

Take those to heart, as if you play in a dynasty league, it's a trend about which to be mindful. That's not to say that older players cannot contribute -- Rajai Davis (37th on the Player Rater), Nelson Cruz (50th), Rich Hill (51st), Carlos Beltran (73rd) and John Lackey (82nd) joining Ortiz as compelling such examples -- but it can be swift and unexpected when a dynasty roster's average age creeps up on you.

There's never any shame in rebuilding, and while contending should always be your goal, recognizing when you cannot win can be as important a skill in a dynasty league as winning. Likewise, knowing when your dynasty league's trade market is softest and certain to provide the richest prospect haul is also critical. Be aware, too, that these decisions are not necessarily coincidental.

Generally, the All-Star break represents, roughly, the time of year you can expect either of those stages to arrive. Trade season will only continue to heat up, especially in ESPN standard leagues where the trade deadline is less than a month away.

To provide a head start, below is the midseason update of my Dynasty 250, which serves as an effective "price guide" for those evaluating trades in keeper leagues.

The rankings formula

The Dynasty 250 uses the following player evaluation formula:

• 2016 second-half performance: 10 percent
• 2017 performance: 22.5 percent
• 2018 performance: 22.5 percent
• 2019 performance: 22.5 percent
• 2020 performance and beyond: 22.5 percent

The rationale for these weights is to provide the most accurate long-term projection of the player's value, essentially identifying the wisest, safest long-term investments. In addition, the reason that 2020 gets a greater weight than the remainder of 2016 is that I already provide Going Forward Rankings for fantasy owners focusing solely on this season. They are published weekly, most recently on July 6 with the next one scheduled for July 20.

Remember that other factors influence these values, beyond simply your league's scoring system. The list below is a starting point, but you need to do your own manual adjustments to account for the following:

• Number of keepers: How many players can you keep, and must every team keep the same number of players?
• Player pricing: Is your league draft or auction format, and do you keep players in the round they are picked, for the auction price paid, or are players simply kept without prices attached?
• Contract factors: Are there limits on the number of years you can keep a player and/or are there guaranteed contracts, and is there price inflation?
• Farm teams: Does your league include minor leaguers and how are these players factored into the keeper system?
• Team competitiveness: Are you a contender, rebuilder or something in between? At midseason a firm answer to this is much more crucial.

The Dynasty 250

Note: Position eligibility ("2016 Elig. Pos.") is determined based on a minimum of 20 games or the position the player appeared at most often in 2015, or 10 games played at a position in 2016. Players' projected future positions are considered in the ranking. Players' listed ages are as of July 15, 2016.

Players' 2016 preseason ("Pre 2016") and peak rankings in past keeper lists ("Prv. Peak") are also provided: These lists have been published semiannually since 2010, with "preseason" and "midseason" designated to differentiate the different times of the years in question. For example, Jon Lester is listed with a peak of 17 in "Mid-10," meaning that his best all-time rank was 17th, in the 2010 midseason list. A "--" means that the player has never before made the cut.