I recently wrote an article comparing the Cubs’ two leadoff hitters, Ryan Theriot and Kosuke Fukudome, in which I ultimately came to the conclusion that Theriot was the better option to hit atop the batting order in large part because Fukudome might find himself on the bench before too long.

Shortly thereafter, Lou Piniella decided to replace Theriot at second base with Mike Fontenot and said the move might “be more than a one day thing.” Suffice it to say that I wasn’t feeling too smart when that news came across the wires.

I’m not against the move.

Fontenot is a good ballplayer and has played well enough to deserve a starting spot that isn’t dependent on Aramis Ramirez’s injury status. And since Fukudome hasn’t found himself mired in a complete slump yet, he should be able to hold down the leadoff spot.

I just think that Theriot is a much better ballplayer than his current statline would suggest, so I looked for a reason that he might be underperforming. The data that I was looking through led me to believe that he was being pitched differently and having a little bad luck.

It wasn’t until Tuesday’s game against Pittsburgh that a much more likely explanation finally surfaced for me, courtesy of Pirates broadcasters Tim Neverett and Bob Walk.

Maybe I’m the last horse to cross the finish line on this one, but Theriot’s slump appears to have begun the day he shifted to second base.

I know that correlation doesn’t imply causation (insert Statistics 101 reference to ice cream sales and drowning rates here), but it’s a very interesting correlation, to say the least.

Before Starlin Castro was called up on May 7, shifting Theriot to the keystone, the Cubs’ scrappy leadoff hitter had a slash line of .341/.374/.390 in 182 plate appearances.

More specifically, Theriot was on a tear in his last 15 games at short, boasting a slash line of .435/.458/.507 in 73 plate appearances. That’s an almost Pujols-esque OPS of .966 for a little over two weeks.

From May 7 until now, his slash line is a scary .205/.224/.205 in 86 plate appearances. Two times hit by a pitch, no walks, and no extra base hits.

He just stopped putting up any numbers whatsoever.

Now, with this in mind, I looked back at his swing rates for the season on FanGraphs. This time I focused on his swing rates relative to the strike zone instead of overall swing rate to take a closer look at his approach at the plate.

Sure enough, I overlooked something potentially important in my previous research.

Theriot’s overall swing rate is the highest of his career by less than one percent, which I noticed before. If I had taken a gander at a column just to the left of that information, though, I might have seen the larger problem.

This year, “The Riot” is swinging at 24.3 percent of pitches outside the strike zone. For his career, including this year’s higher-than-normal rate, that number sits at 20.8 percent.

Although it’s not a huge difference, it seems significant enough that it might signal that something’s wrong.

As far as I know, there is no resource that allows you to break down this information by date, so I don’t definitively know if there is a difference in swing rate rate before and after Castro’s call-up.

But it wouldn’t surprise me in the least if the rate he’s posting right now is inflated by what he’s done in the interim.

Maybe he’s adjusting to the move back to his old position and carrying that adjustment over to batter’s box. Maybe he’s been pressing because playing time among the corps of middle infielders is being spread a little thinner. Maybe it’s a little bit of both.

Or maybe I’m just an eternal optimist.

At the moment, I think that Theriot just needs to relax and be the player many Cubs fans have come to love.

Maybe that will finally happen with him out of the starting lineup.

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