Yesterday, the Marlins called up Carter Capps from the minors, and Capps went on to make his season debut in last night’s game against the Braves. He pitched well, getting all three batters he faced out, one of them by strikeout. But a reliever getting called up and throwing a scoreless inning isn’t worthy of a post, so you know there has to be more to the story. And there is, because here’s what Carter Capps throwing the ball looks like.

legal pitch or nah? pic.twitter.com/sdNI4dXrky — nick pants (@nick_pants) April 14, 2015

Jordan Walden has been doing this for years, but Capps looks to be taking the jump-towards-home-plate delivery to an entirely new level. He had a reduced version of this delivery when he got to the majors with Seattle, so this isn’t entirely new, but the jump-step he showed last night goes beyond what he did in his previous big league stints.

When he was traded to the Marlins — he was the return for Logan Morrison — he noted that he wanted to change his delivery, or perhaps more accurately, walk back some of the changes he made in Seattle.

“I’m trying to get a little more use out of my legs, like I used to pitch,” Capps said. “When I went to Seattle, I changed some things around. I’m trying to get back to pitching the way I used to pitch.”

Get a little more use out of his legs, indeed. Mission accomplished, sir. But is this really legal? PCL umpires didn’t think so, when his first two pitches in an appearance last week were ruled automatic balls for “disengaging the rubber”. But if you look at the MLB rules, there’s nothing actually in there that says your back foot has to remain on the rubber when delivering a pitch to the plate.

In MLB’s official rules on the “legal pitching delivery”, the phrase “disengaging the rubber” is used, but only in regards to what a pitcher can and cannot do with regards to pickoffs. For instance, it specifies that a pitcher must drop his hands if he disengages the rubber — in order to show that he’s no longer preparing to throw a pitch — but there isn’t any wording in there that says you cannot disengage the rubber during your natural throwing motion.

The fact that Walden has been doing this for years without punishment set a precedent that it was legal, and Capps even got assurance from MLB that his delivery is indeed allowable.

Marlins reliever Carter Capps received some clarification from Major League Baseball regarding his unorthodox delivery, where he takes a small hop off the rubber. Basically, it was pointed out to the reliever to not elevate so high. Capps’ mechanics came into question last Thursday, when he was pitching in the ninth inning for Triple-A New Orleans. Each of Capps’ first two pitches against Omaha were called illegal pitches, resulting in automatic balls. Rather than have Capps change his delivery, which could lead to injury, he was instructed to intentionally walk the batter. After the four pitches, Capps was replaced. The next day, the Marlins contacted Major League Baseball seeking clarification on what Capps, who has 88 games of big league experience, was doing wrong. “They just said they wanted me to make sure I dragged my foot and not get too elevated in the air, and make sure it’s more on a lateral plane,” Capps said. “As long as I do that, they have no problem with it. But it was very strange.” … “It doesn’t look pretty, obviously,” Capps said. “But that’s the first time anybody had a blatant problem with it. They didn’t want me to get too much elevation. They understand I’m going to come off the rubber, but they wanted me to drag my toe a little bit more. I’m going to try to do that.”

So, according to Capps, jumping forward is okay, but jumping up is not. The league clearly knows their rulebook a lot better than I do, though I will admit that I was unable to find anything in the rules that would be the basis for that conclusion. That doesn’t mean it isn’t in there. Perhaps there is an addendum to the delivery rule that simply didn’t make its way online. This isn’t an area where I’m going to claim to have any kind of insight, because I’m not a rules junkie, and I’ve never umpired. If MLB says it is legal, then it’s legal.

Walden has been a very effective Major League reliever, and like Capps, he’s been able to sustain excellent velocity even while jumping towards the plate during his delivery. For his career, Walden’s posted an 82 ERA-/71 FIP-/84 xFIP- line, with an average fastball velocity of 96.6 mph during his career. However, Walden’s ability to miss bats has been offset by command problems, and as Eno Sarris wrote here a couple of years ago, there are reasons to think that the jump-step could be partially the cause of Walden’s inability to throw strikes consistently.

In his previous big league appearances, Capps’ walk rate was okay, and he threw 50.6% of his pitches in the strike zone, a few ticks higher than Walden’s career 47.7% mark. But he didn’t used to leap forward like this, and it’s possible that the trade-off for getting a release point closer to the plate will be some reduced ability to throw strikes.

But it’s probably worth trying out, especially if it helps solve his problems with left-handers. His arm-slot and his slider already makes him really tough on right-handers, but he’s been lit up by lefties in the big leagues, giving up a .404 wOBA to the 201 LHBs he’s faced in his career. To this point, Capps has essentially been a righty specialist; he doesn’t really need to the jump-step to dominate RHBs, since his repertoire already allowed him to do so.

But since he doesn’t really have a good out-pitch against lefties, his best bet against LHBs is probably to try and overpower them with fastballs. 97 from a low arm-angle hasn’t been good enough; 97 from a low-arm angle released at the very front of the mound might be. Walden actually has been better against LHBs than RHBs in his career, though he has started incorporating a change-up into his repertoire of late, so it might be more of a pitch quality issue than a release point benefit.

But it probably doesn’t hurt to try. Walden didn’t always throw many change-ups, and he was effective enough early in his career to close for the Angels with mostly just velocity and a jump-step. For Capps, this isn’t a bad role model to emulate, especially if mastering a pitch to equalize left-handers doesn’t seem to be in the cards for him.

If it works, and Capps turns into a quality reliever, I wouldn’t be surprised if we see more fringy bullpen arms trying this kind of delivery out in the future. After all, reducing the distance in flight gives the batter less reaction time, and if pitchers can effectively throw from the end of the mound, they’ll have an even larger advantage than they do already.

Which is why I’d expect MLB to eventually change the rule if this becomes popular enough. The offensive decline of the last few years isn’t showing any signs of slowing down, and giving pitchers another way to get an edge over hitters is probably not in the game’s best long-term interest. But for Capps, it might be a way to convert himself from a right-handed specialist into a potential late-inning weapon.