Should pitchers throw their “best pitch” a higher percentage of the time? I asked that question a number of times this past season, but with a qualifier. Fastballs — most everyone’s primary offering — weren’t the focal point. Secondary pitches were. Think Lance McCullers’ curveball (which he threw roughly 50% of the time this year). Andrew Miller’s slider (61%). Deolis Guerra’s changeup (45%). Zach Putnam’s splitter (68%). Would it behoove more hurlers to up their usage in a similar fashion?

White Sox pitching coach Don Cooper is one of the people with whom I broached the subject. Our conversation came in mid-summer, at Fenway Park, one day after Putnam threw 15 splitters in a 20-pitch relief outing.

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Cooper on Zach Putnam: “He’s coming in for one, maybe two innings. We want him to command his fastball. But his fastball is not the reason he’s in the big leagues. His split is. If we’re going to win or lose a game, it’s going to be on the split more often than not. He uses the fastball to locate, and get them off splits. He uses it to protect the split.

“He’s on the DL right now, because he’s had some difficulty recovering, but listen, we’re not bringing him in to throw fastballs. If that’s what we wanted, we’d leave the starter in, because I guarantee you that whatever starter we have in has a better fastball. We’re bringing him in because his best pitch is the split. He’s been striking out a guy an inning, and he hasn’t been doing it with fastballs.

“He did probably get a little top heavy with splits last night. He was coming off them. That was the problem. He wasn’t staying on it, so they weren’t quality splits. But again, I want him throwing his split. I also want him to use his fastball and his cutter to keep the hitters honest. We’ve seen in the past that if you throw too many splits in a row, the hitter will get on them a little bit. They’ll know what’s happening and hang in there better. That’s where a fastball, in, will get them off the split.”

On Jose Quintana and Chris Sale: “[Quintana] wasn’t always that way, but the curveball has become a big pitch for him. Listen, whatever a starter’s second pitch is, it’s going to be thrown the second-most amount of times. He’s fastball, curveball, cutter, change. His curveball is his second-best pitch and his fastball is first. So, you’re going to see a fairly decent number of them.

“If it’s a really good pitch for you, you’re going to use it a lot. Chris Sale, the last three years, has been lots of changeups. Fastball and lots of changeups. But what happened then is, people started being able to deal with just two speeds. That’s when we started using more breaking balls. Now there are three speeds to deal with. If you’re locating your pitches, changing speeds, getting ahead, you have a chance to be successful.”

On asking pitchers to throw a particular pitch more often: “I’ve told Putnam that I want more splits. That’s the pitch that’s going to enable him to have a career. It’s not the other way around, throw a lot of fastballs and a few splits. But anyone else? Let me think about that. No. I don’t think I’ve ever told another pitcher, ‘I want you to use this pitch a lot more.’ Offhand, sitting here right now, I can’t remember doing that.

“I like the breakdown. To me, a starting pitcher… if you’ve got four pitches that you can throw strikes with… that’s what you want. Everybody thinks you can dominate a game with velocity. Last night, Miguel Gonzalez didn’t dominate the game with velocity. He did it by four pitches, throwing them all for strikes and changing speeds. Mark Buehrle, who I had for 10 years, never dominated a game with velocity. He did it with movement, location, and changing speeds.”

On velocity and pouring in strikes: “Velocity only gets people out so long. Josh Tomlin, in Cleveland: he’s got very good pitchability, not unlike Miguel Gonzalez. None of their pitches are going to raise your eyebrows — ‘What a great fastball, what a great curveball’ — but they’re all solid. When they locate them and get ahead in the count, they can be very tough.

“I’ve had a lot of guys over the years, and the best ones — and the best ones I’ve seen on other teams — forget about stuff. Forget about velocity. The No. 1 thing they do is pour strikes in. They’re dictating the game. They’re coming right after the hitter. If you look at games that are dominated… if you look at USA Today and see that somebody pitched really well — let’s say he went seven innings and threw 100 pitches — I guarantee you he threw two-to-one strikes to balls.

“There are certain numbers I’ve always gone by. First-pitch strikes, 1-1 strikes, first batter retired, percentage of fastballs, curveballs, sliders, changes thrown for strikes. And the speed difference of those pitches. That’s the meat and potatoes for me.”

On speed differential: “Do I like it? Absolutely. Look at the knuckleball pitcher last night [Steven Wright] threw some fastballs 87-88. He threw some knuckleballs at 63. He threw some knuckleballs at 77. He was only using two pitches, but he was changing speeds. He was making the hitter, ‘Ooh.’ He was making him think.

“Changeup differential… do you know what? The hitters will tell you. Their swings and their approaches will tell you if it’s soft enough. For me, the bigger the differential, the better; but I’ve seen plenty of changeups that were 6 or 7 mph off the fastball, and that’s fine. It’s not essential to have a certain differential.”

On swing-and-miss rates: “Do I care about them? Not really. I care about what they’re doing with their pitches for strikes. If we throw strikes and the hitters… and I like ground balls, too. The best pitched game for me is 27 pitches and every one of them was hit into the ground. Swings and misses? I like them, but first and foremost, I like strikes. Quality strikes.

“Chris Sale has a good swing-and-miss rate on his curveball, but we’re not going to throw 60 of those. It’s not only a health thing, but after awhile, if you throw the same pitch over and over, they’re going to be looking for it. Again, you have to mix it up. Put elements of doubt in hitters’ minds.”

On Jose Quintana’s expanded repertoire: “From the first year on, [Quintana] has added some things in there. At first, he was fastball-cutter. Then we played with a curveball, played with a changeup. Now he’s got four pitches. He can elevate his fastball. He can do a lot of different things. But the foundation of it all is a very good delivery that can promote more and more strikes.

“A lot of people don’t know Quintana, but we do. He’s been good for four years. He hasn’t gotten a lot of wins for us, because he leads the world in no-decisions. That’s not his fault. The bottom line is that he takes care of his job every time he goes out there. The reason he can do that is because he’s coming at people. He works hard, changes speeds, and he has four pitches.”

On putting the percentages in your favor: “If you go out there tonight — you, personally — and just toss it in there, you’re going to get a certain amount of guys out. There are people behind you. And if you can locate, you’re going to get another percentage out. If you can throw a second pitch for a strike, that’s another percentage. If you have stuff… same thing. The percentages start adding up in your favor.

“If you have one really good pitch? You’re not going to be a starter. You’ll be a reliever. There are plenty of guys who come in and throw slider, slider, slider. [Luke] Gregerson, in Houston. He throws a boatload of sliders. It’s his best pitch, and whatever your best pitch is, that’s what the majority are going to be. That’s for a reliever. Starters have to mix it up. But a starter’s best two pitches… you’re going to see them a lot. You have to throw your best pitches.”