An older player with diminishing skills, for example, can't be judged by a mathematical average. His skills are no longer at their average level.
Similarly, a young player with a short career, non-full time play, large fluctuations from year to year, cannot be evaluated by a mathematical average. Averaging in two or three very different performances tells us nothing.
In Heisey's case the critical factor IMO is the enormous change (to the downside) in his performance with more PAs and the passage of time. It indicates to me that the league has figured him out and that the flaws are not being overcome.
Heisey used to hit righties better. Now he hits lefties better. He used to hit for power. Now he doesn't hit for much power. His overall performance was OPS+ 100 or above. Now it's well below. And last year his .22 BB/K rate was very poor, down there with Valdez and Cairo. These are more important indicators to me.
The question in such a case is why? My view is that he is a fastball hitter and overly aggressive at the plate. Pitchers get him out by mixing pitches and making him swing at bad pitches. Chris complies.
I thought maybe, with maturity, this season would be different. I was hopeful when he took over LF. At this point, I think the Reds have to begin to think about other options who can handle left field most of the time this season.
Not because of Heisey's 2013 start alone. But because of Heisey's trend line. Regardless of his mathematical average.