I/O:  Jeff Sullivan, typically, understates his own insight in this piece about Robles' foot plant.  All that he's got goin' on, and humility too.  Wotta guy.

Sully affirms that Robles' foot plant is, firstly, important:

Look at Robles' back leg. Then look at his front leg. Then look at the catcher.

Ordinarily, these three points are supposed to arrange themselves in a ~line. Check out Roy Halladay as an example. This is what's called the driveline, and as much energy as possible should be going towards hurling the ball along it from the rubber to the plate.

Robles' right leg, though, doesn't swing all the way around to the line, instead stopping short at a...70? 80? degree angle. To make sure this wasn't a one-time fluke, I looked at some video available here and here, and, sure enough, it's consistent. Robles' right leg is very frequently - if not always - kind of off to the first base side there, turning the driveline into a triangle.

Blinkin' right it's important.

... and LL serves up these impressions as to the consequences:

Having a front leg that lands too 'closed' can serve to inhibit forward momentum. The pitcher can end up kind of throwing over his leg, and he will have difficulty getting good forward extension. This can manifest in lower perceived velocity, difficulty in achieving a consistent release point, and difficulty in staying low in the zone. With the leg off to the side, there is no smooth delivery straight from the mound to the catcher. There's a delivery that's forced to compensate for a little resistance, and that can make it very, very hard to release the ball as far forward as you'd like.

There's also the risk of knee damage, as the knee is twisting and taking force and everything.

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CRUNCH:  Robles is "coming around the corner" at the hitters.  This is something that some ML pitchers, and some very good ML pitchers, like to do.  Most of them are relievers, like Jeff Nelson

... but Jered Weaver (for example) comes around the corner a lot -- check out the chaotic lower-body action in the photo.  You'll remember El Duque.  A lot of the Cubans do this.

This "around the corner" mechanic has, in aiki terms, theoretical plusses and minuses.  More minuses than plusses. 

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1.  The angle can be hellaciously deceptive, especially on breaking pitches, and the spin on the ball can even increase.  Think Jeff Nelson.  Even in PBNW's couple of videos, you could sense how viciously the ball was angling across the zone.

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2.  Absolutely the mechanic costs you horsepower to the back wheels.  Think about short-arming:  much more deceptive, but much less leveraged.  Those pitchers who can get away with it, who can make it work, have an advantage.

Can David Aardsma keep hitting 96 with short mechanics?  Okay, if he can, he's got +2 feet via deception.

Robles is fighting his own body, as it were, but for those pitchers who make it work (like Jered Weaver) they've got an advantage.

All of Sully's observations about the random release point, the ball up in the zone, etc., we absolutely agree with.

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3.  Sully wonders about lower-body issues.  Well, Robles is a pretty heavy guy, too.

Whether injured or not, a lower body with such illogical movement can fatigue, as with Phillippe Aumont when he was a Mariner.....

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4.  Note Robles' locked front knee in the photo.  That's the worst part of a cross-step.

So the guy has excellent acceleration, but then poor deceleration.  Poor deceleration is one of Dr. D's pet peeves, though some ML pitchers do finish with locked front knees.  Decleration is part of the natural aiki spiral.  It's part of harmony with nature.  Guys who stick the landing are abominations of nature :- ) though some make the All-Star game that way.  How good would they have been without the car crashes at the end of every pitch?

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SSI wouldn't call the mechanic "incorrect" any more than we would call short-arming "incorrect."  Both are theoretically inefficient, but in practical terms can add to deception.

No doubt Mauricio leaned around the corner one time :- ) and WHOOP!  batter fished horribly .... he came around the corner again and got a tremendous rip into the spin on the ball and .... boom, it's working for you, you start leaning more and more to 1B and isn't this fun.

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In Robles' specific case, am guessing that the cross-step is causing the early fatigue.  All things considered, if I'm the M's, I'm listening to LL on this one.  Coupla bullpens where Mauricio has to step on the correct side of a flat garden hose, and he's right as rain.

Jolly good shew,

Dr D