Josh Hamilton thinks his eye color is the cause of his hitting problems during day games, and at least one optometrist agrees with him. After initially thinking it was just talk, the idea that there could be some scientific explanation that explained his problems made this story more interesting. So, the next natural step was to look at some data.

On Friday, we asked you guys to come up with blue-eyed players, and you responded with enthusiasm. Over the weekend, I went through that thread and looked at all the nominated players, compiling a list of guys who might make for a useful comparison to Hamilton. I left out players who played a significant part of their career in a dome, for instance, and left out guys who were noted sunglass/tinted contact lens wearers, as we wanted to measure the performance of light eyes in day light with as few compounding factors as possible. Overall, I came up with 25 players who fit the criteria. It doesn’t sound like a huge number, but those guys combined for over 47,000 day-time plate appearances and over 100,000 night time plate appearances in their careers, so sample size shouldn’t be a problem.

The results? Well, you probably won’t be too surprised.

During the evening, these blue-eyed players combined for a career mark of .280/.363/.472. During the day, they hit .282/.364/.475, almost exactly the same as they did when it was dark out. This non-difference matches up with the rest of the population, as there is no consistent historical day/night split for Major League hitters over the years. The sample of blue-eyed players we looked at follows the trend established by the rest of Major League Baseball.

The group split right down the middle, with 13 players posting a higher OPS in the evening and 12 players having a higher OPS in the afternoon. The full list of players and the data can be found here.

Of the guys who hit worse during the day, the biggest differences go to Casey Blake (.688 day OPS, .815 night OPS), Tim Salmon (.836/.900), and Chase Utley (.863/.905). On the other side of things, J.D. Drew (.904/.864), Scott Brosius (.771/.729), and Mark Grace (.844/.804) all had the largest positive day/night splits.

Grace is perhaps one of the most interesting cases, as his eyes are very blue and he spent the majority of his career with the Chicago Cubs, who play more day games than any other franchise in baseball. If having light eye colors led to significant struggles during the day time, Grace should have been the most affected player in baseball. Instead, he thrived during day games. I looked to see if there was any kind of obvious career trend that came from perhaps an adjustment later in his career after his eyes got used to all the day games, but, no, he was a good hitter in the day time even early in his career.

Now, I don’t mean to suggest that the optometrist is a crackpot or that there’s nothing to what Hamilton is saying. Certainly, medical experts know far more about how eyes react to sun light than anyone writing for FanGraphs, and only Hamilton knows exactly what he sees during the day and at night. But history does seem to suggest that if there’s a negative impact on blue-eyed players in day games, previous players have found a way to overcome it without it hindering their performance.

And, from a logical standpoint, that makes sense. Nearly every kid on earth grew up playing exclusively day baseball in Little League, and even at the high school level, almost every game for most teams is played in sun light. Practice is always during the day. The batting cages that took all of our money as kids? Only open during the day time.

Night baseball is the exception until a player becomes a professional. Nearly every player in the big leagues was trained to hit a baseball in sunlight, so those whose eye color really does hinder their ability to hit the ball in day light will likely be weeded out long before they ever make it to the big leagues. The structure of amateur baseball would essentially act as a filter, removing players who can’t see the baseball well in day light.

Maybe Hamilton is the outlier here. Maybe his eyes are especially sensitive, and he’ll sustain a large day/night split going forward. It seems more likely, however, that we’re just looking at noise generated by looking at a sample of fewer than 600 career plate appearances, and Hamilton was looking for a reason to explain something that goes beyond randomness.

He’s not the first blue-eyed player in baseball, and history suggests guys who had similar eye colors have done just fine in day games over the years. The Rangers (and Hamilton) would do well to not spend too much time or effort on fixing this problem – smart money says it will probably just go away on its own.