Mariners Could Get More Than They Expect from Sam Tuivailala

In Sam Tuivailala, the Mariners picked up a quality, controllable reliever at the trade deadline, but he does come with some question marks. Dealing relief prospect Seth Elledge straight up for Tuivailala echoed last year’s Tyler O’Neil-Marco Gonzales swap albeit to a much less risky degree, and Jerry Dipoto and Co. are hoping they cash in just as handsomely.

As it stands, Sam Tuivailala could be a fine right-handed specialist. A ROOGY, if you will. He fared very well against righties in 2017, and he has been equally as good this year, holding them to a weak .225/.256/.291 (.240 wOBA) line. That performance made him a clear target for the Mariners and an impactful deadline buy, yet that impact appears limited. Tuivailala’s performance against lefties has regressed to the point of capping his usefulness, but he has the tools to become a full-inning, high-leverage arm.

That is if he can find a little of 2017 in him.

First, we should note that Tuivailala has his velocity back.

The first few games of the season, Tuivailala wasn’t quite himself. His velocity was down around 92-94 mph before he was shelved with a left knee sprain on April 13th. But since his return to game action on May 6th, his velocity has been steady around 95-96 mph and he has dominated right-handed batters (.208/.234/.280/.226 wOBA).

Even at full-speed though, Tuivailala has struggled to put away left-handed batters.

In 2018, 67 LHBs have slashed .357/.463/.571 (.436 wOBA) against him. And as poor as that is, it does stand in stark contrast to last year’s effort. 

In 2017, 62 LHBs slashed just .222/.323/.370 (.286 wOBA) against him, but a large contributor to that success has completely abandoned him this year. 

Tuivailala has seen his command evade him as he has relied more heavily on his sinker.

Source

Against either handedness, Tuivailala has opted for his sinker/2-seam fastball more often than his 4-seam fastball and far more often than last year in general. In theory, this is a fine idea, but take a look at Tuivailala’s sinker heatmap vs. LHBs from this year and last.

Those previously well-located sinkers have crept up in the zone and have leaked over the inner half of the plate, and this has led to disastrous results for Tuivailala, as lefties have an astonishing .433 wOBA on his sinker this year. It is still a solid pitch low or on the outside part of the plate, but getting it there has curiously been a major problem.

It’s possible Tuivailala’s release point is in an unnatural slot right now.

Here are Tuivailala’s average release points by year since 2015 (only 1 IP in 2014).

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Previously, in terms of averages, his highest vertical release point came with his furthest horizontal release point, and his lowest vertical release point came with his closest-to-center horizontal release point. And compared to last year, his average release point is roughly an inch lower and an inch further to his arm side.

These small fluctuations are well within the scope of natural variance, but that Tuivailala is currently sporting both the lowest average vertical release point of his career and the furthest average horizontal release of his career seems unnatural.

This is might be a lingering flaw that he adopted early in the season when his velocity was down, and it could be detrimental to his command of the ball.

This evidently has not posed an issue against RHBs — his stuff plays much better against them — but LHBs are thrashing every offering Tuivailala can come up with. The xwOBA of each of his pitches against LHBs is up substantially from last year and his overall .397 xwOBA against them suggests that luck has little to do with his poor performance.

But his upside is fantastic if he can return to what made him so great in 2017 when LHBs had just a .286 xwOBA against him. Assuming his success against same-handed batters continues, being able to hold lefties to even around a league-average batting line could make him nearly a present-day Pedro Strop. He can continue to function as a right-handed specialist but there is also a non-zero chance he could solidify himself as the bridge to the 8th inning.

Without the same command he previously displayed though, Sam Tuivailala will be reliant mostly on pure stuff, and while that may be enough against righties, his breaking balls aren’t so good that the threat of them can keep lefties off his fastball and sinker. If he has trouble locating the hard stuff, he’s going to have a difficult time competing outside of favorable matchups. That may be fine for the Mariners right now, but they have to want more and the tools are there to make it happen.

All stats referenced prior to games on 08/06/18