Hisashi Iwakuma has thrown his slider 63 times this season and given up four homers and two doubles; he admits the pitch hasn’t been working well for him.

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When Hisashi Iwakuma faces the Angels on Saturday evening, something to monitor will be his usage of his breaking pitches, particularly his slider-to-curveball ratio.

The veteran right-hander can and will throw either in a game, depending on the situation.

But for optimal success, it might be best for him to limit his slider usage, based on past results. Put simply, the pitch hasn’t been effective.

In his last outing, Iwakuma served up a career-high four homers — two of which came off the slider.

Thanks to Pitch F/X date and the websites BrooksBaseball.net and baseballsavant.com, the usage of Iwakuma’s slider and the results are easy to track. And the numbers, well, they aren’t good. Iwakuma has thrown the slider 63 times this season and given up four homers and two doubles — that’s a .546 batting average when it is put into play.

When it is hit, its exit velocity off an opponent’s bat is 95.2 mph. By comparison, the exit velocity for his fastball from opponent’s balls in play is 76.4 mph. When his slider is hit, it’s hit hard. Iwakuma has made just four starts this season, so it is a small sample size. But the slider wasn’t a plus pitch last season. Opposing hitters batted .311 against the slider with a .556 slugging percentage, including six homers and four doubles.

Beyond the numbers, the pitch at times looks flat and without movement.

Iwakuma knows the pitch has been subpar.

“When you look at my mechanics, I tend to fly open more on the slider and I leave it up in the zone,” he said through interpreter Antony Suzuki. “I just leave it spinning and inside to righties, and it’s a problem.”

Of the 10 homers he’s allowed with slider in the last two seasons, seven have been by right-handed hitters.

“It’s unfortunate on the ones he’s thrown that haven’t been too sharp,” said his catcher Mike Zunino. “He’s thrown a couple that have been pretty good. He actually throws it really well backdoor to lefties. ”

The unpredictable nature of the pitch is a problem.

“It’s hit or miss,” Zunino said. “He throws a few of them and you are like, wow, that’s a really good slider, and sometimes it just backs up on him and it gets hit.”

At this point, wouldn’t it be logical to put the pitch in his pocket for a while until he gets some command back with it?

“I have some things in mind, but I’m not going to tell you what I’m going to do,” Iwakuma said.

Obviously, he doesn’t want to give away his own scouting report. He could go to his seldom-used curveball, which he’s thrown just eight times this season. It’s not an outstanding pitch, either. But it might be a better option.

“When you look at my curveball, it’s a 12- to- 6 curveball, and I need to keep it down, and I have not been keeping the ball down like I want to,” Iwakuma said.

But he needs a third pitch.

“You want to keep the batters off balance,” he said. “Having the curveball or slider makes a big difference because it changes speed a lot. And the way the ball moves is very different compared to my two-seam fastball and splitter. It’s a very important pitch. It helps me in the sequence of pitches.”

Zunino is on board with whatever Iwakuma wants to do. But he knows that whatever breaking pitch he decides to use, Iwakuma must have some conviction when throwing it.

“It’s comfort thing and if he’s not comfortable throwing it, then we shouldn’t,” Zunino said. “I want him to have 100 percent confidence in whatever he’s throwing. If you have to put it on the shelf for a start or two until he can find it in the bullpen, then we may have to do that. If he has conviction when he’s throwing it that makes the world of difference. If he’s in between in his belief on throwing a pitch that could lead to him throwing a pitch that’s not as sharp.”