This morning, Parkes unveiled a terrific post on Colby Rasmus’ struggles at the plate in 2011. He pointed out some mechanical flaws and an increasing inability to lay off/do anything when thrown changeups away in the zone.

In some of the great discussion that followed got me thinking about Colby Rasmus’ at bats. Certainly waving at change ups isn’t good for business but there must be a deeper meaning behind his inability to make do with faded changes away. I think the reason for this struggle is simple: he has backfoot slideritis.

Backfoot slideritis effects even our most prolific sluggers. The “book” on Jose Bautista is he is vulnerable to the power sliders of big, hard-throwing left-handed pitchers thrown down and in. With all given small sample size alerts in mind, his lack of success against a pitcher like CC Sabathia speaks to the gigantic Yankee ace’s ability to exploit such a hole. There you go, world: all you need to get Jose Bautista is one of the top four pitchers in baseball. Make sure he is left-handed and throws an 88 mph slider. You’re set.

Colby Rasmus is not Jose Bautista but my memory seems to contain multiple examples of similar backfoot sliders tying him up in knots. Like any good nerd, I wanted to see if this was true. Turns out, it is!

Courtesy of ESPN Stats & Info

Using Texas Leaguer’s information, it doesn’t appear the volume of sliders thrown Rasmus’ way increased terribly. We can see, from right-handers especially, the location shifted inward. How did young Colby fare with this adjustment from the righties of the world? Not so well.

Courtesy of ESPN Stats & Info

Striking! Not exactly a positive trend for Blue Jays fans, is it? That’s a .149 wOBA against sliders in 2011 compared to a .342 wOBA against the slide piece in 2010.

Now imagine you’re Colby Rasmus. You’re slumping. You are behind in the count because, as Jon Hale noted in the comments of Parkes’ post, you can’t do to fastballs what you once could. You see a pitch, looks down the middle-ish. You ID offspeed. But which offspeed pitch is it?

/ends in tears

Is it the slider about to break down onto your shoe tops or the changeup about to gentle fade over the outside corner? Hurry up, pretend Colby Rasmus! You have about a quarter second to decide!

In 2011, Colby Rasmus saw changeups early in the count, most frequently in 1-0 or 0-1 counts. As the at bat grows longer, Rasmus seems more and more sliders from righties. 17% of the pitches throw to Rasmus with two strikes are sliders, second only to four seam fastballs. Rasmus falls behind, is set off-balance by a change up and often fooled by the slider.

The important, non-mechanical question for Rasmus in 2012 – can he adjust to this common approach used against him? Can he improve physically to where he is able to either do something with these early-count changeups or lay off the tough sliders down and in?

A better physical approach to attacking the baseball goes a long way. Using the whole field, all that good stuff, isn’t possible if Rasmus is all in his own way. Better body, better mind, and all the talent are in the world all work in Colby’s favor. The devious breaking balls of American League pitchers will certainly do their worst to prevent Rasmus from reaching his potential. The league adjusted to Colby, now Colby must adjust to the league. It’s part of being a big leaguer. Like most things: easier said than done.