Tip #1: Know where player values come from

Tip #2: Set your Hit/Pitch split

Tip #3: Value your Picks and Make Preseason Trades

Tip #4: Draft with tiers

Tip #5: Using xFantasy, the xStats projection system

Quick editor's note: This is based on my post in the FanGraphs Community blog back in 2016, condensed a bit and with updates for this year. The TL;DR version? Using projections for this year only, you can apply aging curves and calculate player values for keeper leagues!

One of the most oft-discussed and most subjectively-answered fantasy baseball topics is “Who do I keep?” Fantasy baseball players intuitively understand the idea of aging, at least qualitatively. Older players are less valuable, given that their performance is more likely to decrease due to both injury and ineffectiveness. But how much is age worth, really?

Thanks to work by Jeff Zimmerman and Bill Petti (Hitters, Pitchers), we now generally know that in the post-PED era, players only get worse once they’re in the league. It won’t stop people from imagining a Mike Trout 20-WAR age 26 season, but it appears to be true. However, how to translate this knowledge into quantifiable fantasy valuation remained a bit unclear. For hitters, the original work used deltas in wRC+, and Mike Podhorzer (and Jeff) took a look at how steals age, filling in one piece of the 5x5 puzzle. For pitchers, we know how the various component pieces of pitcher performance (K/9, BB/9, velocity, etc.) age, but the most catch-all stat examined would be FIP. In any case, these really only give you a qualitative sense of aging, short of attempting to correlate wRC+ or FIP with 5x5 value and applying those curves directly.