Its well known that its a mistake to believe that just because a player had a good season, he will repeat that performance the following year. Just how big of a mistake is it, though? Maybe bigger than you think.

There were 123 players in the major leagues worth at least three wins above replacement in 2015, going by baseball-reference.coms formula for WAR, which is a fairly standard tally. In this decade, the number of 3 WAR players has ranged from 113 in 2010 to 139 in 2014.

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Of those 123 players, only 65 also were 3 WAR contributors in 2014. It would be tempting to point to the number of young players making leaps forward this year, but the retention rate of 3 WAR players from the Troy Polamalu Hoodies Sweatshirts 2014 season, 46.8 percent, was pretty normal for recent times. Its been as Pittsburgh Steelers Accessories low as 39.7% from 2011-12 and as high as 51.6 percent from 2013-14.

What this means is that as 2016 approaches, its fair to expect somewhere around half and probably more than that of this years good players to slip into mediocrity or worse. Some of this will be a result of injury and some of this will be a result of age, but mostly, its about general fluctuation.

Only nine players have cracked 3 WAR in all six seasons of the 2010s: Jose Bautista, Adrian Beltre, Miguel Cabrera, Robinson Cano, Adrian Gonzalez, Cole Hamels, Felix Hernandez, Clayton Kershaw and Andrew McCutchen. Another 12 have had five 3 WAR seasons, 31 have had four, 50 have had three, 91 have had two and 184 have been one-and-done.

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The trick for front offices in the offseason, obviously, is to figure out which players will tail off and which ones will rise up while constructing rosters for next season. The difficulty is obvious in building a contender from year to year.

The Cardinals, for instance, had a Anthony Miller Jerseys major league-high seven 3 WAR players in 2015: Matt Carpenter, Jaime Garcia, Randal Grichuk, Jason Heyward, John Lackey, Lance Lynn and Carlos Martinez. St. Louis already knows that and will be with the Cubs, while Lynn will mi s 2016 following Tommy John surgery.

Adam Wainwright would figure to be better than a 3 WAR pitcher in a fully healthy year, maybe Michael Wacha brings himself up a notch, maybe Stephen Piscotty has a breakout season, maybe Yadier Molina is great after thumb surgery. That is a lot of maybe in the equation for a team coming off a 100-win season, and thats before you get to the potential for the holdover 3 WAR players to backslide.

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Projection systems can help sort things out by providing a hint of who is likely to rise and fall, but there still will be players like Dee Gordon who appear to be destined to slip, then wind up more than doubling their WAR output from 2.3 in 2014 to 4.9 in 2015.

So, good luck figuring it Najee Harris Jerseys out, because its even harder to tell which baseball players will be good from year to year than you already thought it was.