Good question and I've asked several times in the past if sliders actually work in MoM. Never got an answer. However, if it does have an impact, I'd be happy to see what kind of sliders you use.
I looked at the real life pitching stats for the past season and pitchers threw an avg of 3.92 pitches per plate appearance. In the game it's well above that.
Very rarely do pitchers get through a 1-2-3 inning in less than 15 pitches. Doesn't matter who the pitcher is.
They get a 0-2 count on a batter then proceed to throw out of the zone for the next 3 pitches or so.
They will also get a 3-0 count then throw 2 strikes. More than half the time they walk the batter.
Very rarely do you see a pitcher throw 3 consecutive strikes, and when it happens it's because the batter swung at a bad pitch on the 3rd strike. I think I've only seen one time in my season where a batter was called out after the 3rd consecutive strike. They also rarely throw 4 consecutive balls. Normally it's 3 balls then 2 strikes (some strikes are batters fouling pitches off).
But 5 pitches is not even the low norm considering how many pitches batters foul off so often. In an avg game, pitchers are throwing between 20 & 30 pitches per inning whether they are 1-2-3 or not. IF a pitcher has a sub-15 pitch inning, it's a guarantee within the next couple innings there will be a 35-40 pitch inning. I think the game is programmed to do that to keep pitch counts realistic.
I do think that another way to run pitch counts up is to hit the ball. Get hits. The game seems to prefer batters just standing there with their bats on their shoulder for 4 or 5 pitches. In the 4 years I have played this game I have never seen a team decide to get aggressive at the plate.
The reason I haven't messed with sliders, apart from not being sure if they matter in MoM, is because I'm not sure which sliders do what exactly, and what affect changing one slider will have on another. I know some sliders work in conjunction with others.