Blue Jays in Focus: Inside the rebirth of Aaron Loup’s slider


Toronto Blue Jays reliever Aaron Loup has been a rare spot of disappointment in an otherwise stellar 2015 season, but an overdue demotion to AAA Buffalo gave the lefty an opportunity to work out his mechanical issues. Now back in the Blue Jays ‘pen and pushing for a spot on the playoff roster, it’s the changes made to Loup’s slider that should return him to his 2012-to-2014 form.

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In nine appearances since returning to the MLB roster in early September, Loup has been used in a much more situational manner with nine appearances spanning just 3.2 innings. He’s kept the run column blank over that short span, allowing four hits and striking out four.

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Ideally, Loup’s resurgent slider will help him regain form as a lefty-on-lefty specialist, something that certainly has a role on a playoff roster. Loup’s 2015 has been a clear regression, but his career opponent’s average against left-handed hitters still rests at .208. With an arm angle that can make hitters uncomfortable even on the straightest of pitches, Loup’s violently-breaking slider produces absolute mismatches. To breathe life back into the pitch, he’s made three noticeable changes.

First and foremost, Loup came into 2015 throwing his slider entirely too hard. According to FanGraphs PITCHf/x velocity data, his slider jumped from an average of 77.5 MPH in 2014 to 80.9 MPH this season (a number that was even higher mid-season). Since his return, however, the velocity has returned to its old levels. Where it belongs.

The above graph from Brooks Baseball shows us that all three of Loup’s pitches have taken a step back in release speed, which again, is a good thing. The slider has plummeted to a season-low speed of 76.68 MPH out of the hand from his season-high of 83.67 MPH in July.

When Loup was hanging sliders over the plate in the lower half of the zone earlier in the season, this was the culprit. When reaching the plate so quickly, these pitches had much less time to break and bury themselves down and away from left-handed hitters.

Following the red line through the data above, you’ll notice that the vertical location (how high or low in the zone a pitch crosses the plate) of Loup’s slider has changed drastically since his mid-season struggles. When Loup’s slider was at a career-high velocity in July, it crossed the plate in a very hittable location. In August and September, the slider has returned to its location of old: off the chart and out of the zone.

The question remains, though, of how Loup made these changes so quickly. I’ll argue that one simple change to his vertical release point (the height at which a pitcher releases the ball) helped to spark the decrease in velocity and improvement in location.

From the time when Loup was sent down to AAA Buffalo to his MLB return, the releast points on his slider and sinker (fastball) have dropped substantially. This isn’t by accident. With his slider now leaving his hand six-to-seven inches lower than it had earlier in the year and travelling slower to the plate, it’s staying safely out of the hitting plane.

This isn’t a golden ticket for Loup onto the playoff roster, but at minimum, it should provide some level of context to his early struggles and give hope that he can overcome them, both this season and going forward. Loup’s slow start wasn’t just a case of him “not having it”, it was a mechanical issue paired with a BABIP of .336, a full .090 points over his 2014 total. Loup has taken care of the first issue, so if Lady Luck can take care of the second, he might just land on his feet.

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