Prior to this season, Estrada has been something of a changeup specialist, using his fastball to set up his changeup and using his curveball to keep hitters off-balance. But this year, he's not just using the fastball as a means to an end, but as an actual weapon to get hitters out. Even though his fastball sits at 90 mph, his impeccable control assists him in putting said pitch in places where hitters have trouble doing anything with it. His heat maps tell a pretty convincing story; he's attacking left-handed hitters up and away with his fastball, and throwing down and away to righties.
Pitching primarily with an ordinary fastball is risky business, and when Marco misses it leads to hard contact. But he's missing less this year than in the past, and whether the improved control is due to him figuring it out or just settling in with more consistent usage is anyone's guess. Either way, he's not just throwing strikes, he's throwing quality strikes. And being able to get ahead in the count has made his secondary pitches more dangerous.
The changeup has always been a putaway pitch for Estrada during his time as a Brewer, but this year he's cut back on his usage of it. But that doesn't mean he's lost faith in the pitch or that the pitch isn't effective, he's just using it better. PITCHf/x pitch values claims his change is a little below average, and while I don't necessarily buy that, either way the pitch is still valued higher than in previous years. From watching his starts this year, it appears that he's cut back on using it early in the count, instead saving it to get a needed whiff. This at-bat against Brian McCann is a textbook example
The first two pitches of the at-bat were fastballs up in the zone that McCann fouled off. With McCann down 0-2 and in survival mode, Estrada threw a filthy changeup with arm-side run the McCann dove for and foul tipped for strike three. Estrada put the pitch right where he wanted it, and it drew an awkward looking swing. It's a credit to McCann as a hitter that he even foul tipped it (whiff 19 seconds into this video).
This is probably his most underrated pitch. He has two slightly different versions of it, a sharp 12-6 curve that he gets a lot of sneaky called strikes on, and a slurvy-looking thing that he doesn't use often and seems to still be working on (PITCHf/x does not differentiate between the two). He commands his primary curve well, and will use it in just about any count to keep hitters off of his fastball. Like his changeup, when hitters aren't expecting it it can lead to some ugly swings, like this one from a surprised Michael Bourn (about 30 seconds into the same video).
Do you see the ball? Neither does Michael Bourn.
All told, Estrada has been a bright spot for the team in 2012 and is almost certain to have a rotation spot in 2013 and beyond. Not bad for a scrap heap pickup. And there's still room for growth. The Brewers organization has done a good job in helping pitchers develop cut fastballs, and if at some point Estrada can add a reliable cutter or perhaps a two-seamer, maybe he can become more than the #4 or #5 starter he's perceived to be.