Fantasy Baseball: Slider's development fueling Sean Manaea's surge

The development of a third pitch is often crucial for a young pitcher, and Sean Manaea seems to have found one. Chris Towers takes a look at the young lefty's potential breakout.

As Fantasy analysts, we've gotten pretty good at figuring out the "what" of a player's performance. We can tell you, for example, that Francisco Lindor is hitting more balls in the air this season, because we have stats that track such things. These are undeniable facts, a true record of what is happening on the field.

The "why" is a lot harder to answer. Reporters can ask players why they are doing something, and sometimes we'll get really good explanations for that. Joey Votto is especially good at explaining in minute detail why he is doing everything he does on the field, as he did this week in describing his more flyball-heavy approach to FanGraphs.com's Travis Sawchik. Why is Joey Votto hitting more balls in the air? Because he's trying to. How do we know? Because he told us!

Things aren't always that simple. Sometimes, players won't acknowledge a change in their game, or they don't have a good explanation themselves. Lindor, for example, has explicitly said he isn't trying to hit the ball in the air more. 

Other times, they just don't appear to have been asked about it. This seems to be the case with Sean Manaea, whose biggest change this season has been his willingness to throw his slider to batters of either side. However, try as I might, I can't find much evidence of Manaea talking about it this season.

Manaea has upped his slider usage from around 13 percent last season to north of 20 percent, per BrooksBaseball.net (all pitch data in this piece comes from Brooks.) We know it was a focus of his during the offseason – Manaea spoke often about working to improve his slider in spring training – but the only sign we have that he is feeling more confident in the pitch is the fact that he has used it a lot more often. Especially against right-handed batters, who almost never saw the pitch last season.

Righties saw Manaea's slider just 7.9 percent of the time, and it's not hard to understand why he tried to keep it from them. He gave up three hits on the pitch, all of which went over the fence. His changeup was a much more refined weapon, and he threw it about four times more often to RHB than his slider.

The change is still going to be his go-to pitch to righties, but the slider is much more heavily involved in the early going. He has thrown it 15.3 percent of the time to righties, and has given up just one homer on 94 pitches. Most importantly, perhaps, his whiff rate on the pitch to righties has jumped from 18.4 to 26.6 percent.

Manaea is never going to have trouble dominating left-handed batters. He has limited them to just a .146/.209/.255 line in 150 career plate appearances in the majors. His stuff plays up against them thanks to a deceptive, almost side-arm delivery. However, he's going to face righties around three-quarters of the time, and there's a pretty hard limit on how good any pitcher can be if he's just OK against right-handed batters. That's where Manaea was last season, allowing a .263/.314/.440 triple-slash line against them.

He wasn't bad against righties, but we're already seeing improvements. Manaea has upped his strikeout rate against RHB from 19.8 to 29.8 percent, a mark only Chris Sale, James Paxton and Alex Wood have bested this year among left-handed pitchers per FanGraphs.com. The slider isn't necessarily the main reason for that, but despite using it less often against RHP overall than his changeup, he still goes to the slider with two strikes more, even against righties. It's early, but a near-30-percent strikeout rate against the tougher half of the platoon, to go with a .213/.305/.346 slash line, is the kind of production an elite lefty would claim.

Manaea isn't an elite lefty yet. He still has control problems from time to time, and his 3.91 ERA isn't far off his 3.86 mark from last season. However, Manaea's peripherals are much improved so far, and if nothing else, we're seeing the kind of considerable upside he has when everything is clicking.

As with any young pitcher, it's hard to make definitive statements on what his limited track record might mean moving forward, but there's a lot to like about Manaea these days. And, with his renewed confidence in his third pitch -- and 17 strikeouts in two starts against the Indians and Yankees, two tough lineups -- Manaea looks like he may have arrived. Injury concerns abound, but Manaea also has a 2.63 ERA with 27 strikeouts and only seven walks in four starts since coming back from a shoulder injury, so there don't seem to be any ill effects here.

What we're seeing from Manaea may not end up holding up. Maybe he's just had a few good starts, but could lose his feel for the slider at some point, reverting back to a more predictable two-pitch pitcher. However, this is a very good sign for a talented young pitcher who may just be putting it all together.

Manaea may only be available in shallower leagues at this point, but I would do what I could to snag him where I could. This might be the start of something big.