In early February, the Sox agreed to a one-year, $3 million contract with Latos, who was returning from by far his worst season in the Major Leagues, pitching to a 4.95 ERA in 24 games (21 starts) for three teams.
Latos was a nice bounce back candidate but also came with some on- and off-the-field concerns.
In terms of off-the-field issues, Latos had some personality issues to work out, including speaking out against his own team's front office and training staffs.
On the field, Latos has had issues staying healthy throughout his career, too, with knee problems keeping him sidelined for about the first half of the 2014 season.
In short, it was easy to imagine why teams would balk at signing Latos. However, Latos still had some things in his favor, including the fact that he's was just 28 and was not far removed from a good season with the Reds in 2013, when he pitched to a 3.16 ERA in 32 starts (4.8 fWAR).
At the time of this signing, I wrote:
"The White Sox are taking the upside that Latos offers, as not too long ago he was a very good pitcher...Chicago is teetering on contention, and the addition of Latos, if it works out, could help lean them toward a successful 2016 season."
Well, the signing of Mat Latos could not have worked out any better for the White Sox thus far.
In three starts, Latos finds himself near the top of the ERA leaderboard, allowing just one earned run over 18 1/3 innings pitched, good for a 0.49 ERA. FIP (2.85) and xFIP (4.83) are less bullish on his start, as some regression is expected. Latos cannot possibly keep his ERA this low throughout the season.
Regardless, the question I have myself asking is why? Why has Mat Latos been so dominant thus far?
The answer: the slider.
The slider is Latos' best pitch. Unlike his other pitches, the slider generates more swings-and-misses than the average of that pitch. In the past, Latos has needed to use the slider more than just as a pitch to get strikeouts.
In fact, he's done just that this season, throwing the slider in counts where the batter is ahead 16.3 percent of the time. Last season, Latos did that just one percent of the time.
Overall, according to BrooksBaseball.net, the slider is the pitch that Latos is using 19.05 percent of the time. This is the most he has used the pitch since August 2013, when he threw it 22.79 percent of the time. That month, Latos had a 1.73 ERA and a 28 to 6 strikeout-to-walk ratio in 36 1/3 innings pitched. This cannot possibly be a coincidence.
Three of Latos' 11 strikeouts (27.27 percent) this season have come via the slider. An outlandish 23.44 percent of his sliders have generated swings and misses.
This number is even more impressive in context. According to a FanGraphs article in 2014, a good slider has a 15.2 swinging strike percentage. Even then, Latos was mentioned having one of the best sliders in baseball.
Also, when it does not generate strikeouts, Latos' slider is hard to hit. He has a .067 batting average against when throwing the pitch; 62.5 percent of balls in play are ground balls. These are generally manageable outs. As a result, Latos' ERA remains low.
I'd like to have Mat Latos for $3 million right about now.