[Moneyline]

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What carries more weight early on in a season. The season stats or career stats?

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Neither.

Handicapping using in-season stats is a recipe for bankroll suicide. Not only are you subjecting yourself to being tricked by sample size, but since much of the betting public handicaps this way to some extent, the lines will often be inflated against you. As an example, lets say a 33 year old starting pitcher who has always been marginal to crappy is 4-0 in 4 starts with a shutout in his most recent game. Not only is this scrub pitcher unlikely to keep up this string of good performances for very long, but people will bet him thinking he is "hot" or has suddenly become a drastically better pitcher at an age when nobody becomes a drastically better pitcher, thus making the price on this pitcher worse than it should be.

Using career stats can produce problems if you don't account for a player's age. A player entering his prime will likely outperform his career stats. A player entering his mid 30s will likely perform worse than he did in his prime.

I think the best way to approach this problem is to look at advanced (meaning sabermetric) career statistics in concert with a player projection system like PECOTA from Baseball Prospectus (although there are other good ones as well). As the season progresses you can use in season stats combined with a knowledge of aging patterns to chart the player's deviation from his projections, and thereby get a good guess at how much this deviation is for real and how much of it is due to luck.

When this question was posed last year at this time of the season one "respected" regular of this forum (who I don't think is a winning capper) was vehement in disagreeing with this. That said, I could be wrong and he could be right, or we both could be wrong. Also, there's more than one way to skin a cat. Hope this makes sense.