The story about Greg Maddux might by apocryphal, but it is illustrative of his particular approach to pitching, which relied a lot on psychology, reading the batters body language and using his own to trick the batter into swinging and missing. As a result, he had a long distinguished career, despite the fact that his fastball topped out at 93 mph, very slow by MLB standards.
Good discussion.
I’ll add that there are two approaches to pitching. Few players are strictly one or the other, but there are definite tendencies.
A power pitcher relies on velocity, throwing the ball as fast as possible in order that the batter not have sufficient time to swing accurately. A power pitcher will occasionally throw a “change up”, where he or she gives the impression of throwing very quickly but then throws more slowly than normal.
A control pitcher relies on precision to throw to the corners of the strike zone, in the hopes that the batter will not swing or swing in such a way as to not make solid contact.
I have a memory that maybe someone can back up of a playoff game in the mid 80’s. There was a player on one of the teams that was famous for rubbing out the back of the batters box so he could set is back foot well behind the plate. In the lead up to the series it became a story about how he did this.
So game one comes along, he does his thing rubbing out the line, and the umpire calls time and flamboyantly pulls out a measuring tape, measures where the back of the box should be, and redraws it.
My memory could be faulty on this and maybe it was an all star game or something like that, but my memory of the umpire redrawing the box is pretty vivid.
not as common as in the past but some baseball pitchers cheat by doctoring the ball - they can scuff it with sandpaper or an emery board or use something like pine tar. A pitcher was caught a few years ago adding something to the ball.
also when a ball is hit it is almost always taken out of play because it might be scuffed up. 60 balls are ready to be used in every game .
Such a pitch is (generically) called a spitball, though it’s rarely actual saliva these days (when it’s even done). As noted, it’s typically the application of a substance (like pine tar, or Vaseline), or scuffing the ball. Either is intended to have the same net effect – by altering the surface of the ball, the pitcher hopes to impart an irregularity to its spin and flight, and thus, make it harder to hit.
Gaylord Perry was probably the last pitcher to be well-known for (or, at least, being widely alleged to use) the pitch, and he retired in '83. (FYI, the spitball was, at one time, a legal pitch in MLB, and wasn’t banned until 1920.)
The knuckleball operates under a similar principle: by throwing a slow pitch, with very little spin to it, as the ball heads to the plate, it presents different surfaces to the air, and thus, moves erratically. Not only does the batter not know where the pitch will go, but the pitcher and catcher don’t, either. When thrown well, it can be very difficult to hit, as even if the batter is expecting a knuckler, he’ll be challenged to know where to swing.
It’s a pitch that few pitchers try to master (and, in many cases, those who do only turn to it when they realize that they can’t succeed by throwing traditional pitches) – at present, it looks like the only MLB pitcher who regularly throws the pitch is Steven Wright of the Red Sox, as R.A. Dickey hasn’t pitched in the majors since last season.
Gaylord Perry was open about cheating and he’s in the Hall of Fame, he played over 20 years, most people know him as a Giant. He even wrote a book called "Me and the spitter " .
More than that, in fact, any ball that even touches the ground is replaced be a clean ball. This is to the batter’s benefit, as a cleaner ball is easier to see and hit. (There is also a safety element here, a batter might not see a dirty ball in time to get out of the way)
I loved watching Perry pitch. He undoubtedly did throw some spitballs, though the fact that he wasn’t actually ejected from a game for it (nor suspended for it) until 1982 (near the end of his career) suggest that he was either (a) very very good at concealing it, or (b) talked about throwing the pitch more than he actually threw it. Regardless, he was clearly a master at getting into batters’ heads.
I remember watching him in a game, near the end of his career. It was a hot, humid evening (this may have been while he was with the Braves), and he was sweating profusely – I don’t know that he could have helped but throw a ball with something on it that night. 
The deterioration of the cricket ball during a game is one of the big variables. Different types of bowlers are advantaged/disadvantaged depending on the condition of the ball. There’s a lot of bullsh!t/sage wisdom spoken about it, but it has a definite effect.
There are certain things you can do to alter the rate the ball deteriorates - you are allowed to polish it on your shirt or pants, you are not allowed to add a foreign substance (although saliva is allowed). The seam (a huge aerodynamic consideration in how the ball travels) will flatten and is not allowed to be repaired.
And of course this leads to all manner of cheating, sorry, gamesmanship, regarding how the ball is looked after.
And THEN, there is a new ball provided after 480 deliveries. Well, it’s available, but the bowling team may choose not to use it, if they are doing well with the old ball.
As I said - mostly a combination of bullsh!t/wisdom/science/magic - but it gives the fans something to talk about.
Does there ever come a point where a cricket ball must be replaced? In baseball, it occasionally happens that a strong hit will literally rip the cover off the ball, and it’s hard to imagine the officials going along with it if a bowler said “Nah, that’s OK” to a ball in that condition.
If the ball goes out of shape or starts to fall apart the umpires can decide to replace it. It’s entirely their decision, but they can use bespoke tools that measure the ball to aid them. They will be given a range of old balls to choose from that are of a similar age and they will choose the one that is closest to the condition of the ball being replaced (but obviously without the damage). If a bowling team is really struggling they will often try to suggest to the umpires that they need to examine the ball and replace it, but umpires are wise to this.
Everyone has already answered this, but to put a point on it - you could make the argument that this is pretty much the entire point of baseball. Everything else is just happening on the margins.
also before a ball is put into a game, it is rubbed down with mud to make it less slick. And not just any mud, they use special mud from one place in every major league stadium.
these guys sell the mud:
Yes, no contact is better than some contact from a pitcher’s and manager’s point of view, even if the occasional contact results in a double play or ground out. The ideal is no contact, or very poor contact. It’s possible to have a pitcher get double digit wins by being a ‘contact’ pitcher who puts the ball in play; it’s also possible that a ‘contact’ pitcher is getting away with it by pitching against mediocre teams that chase balls out of the zone and don’t make good contact. That kind of pitcher, if he plays in the right division and league, can go 15-10 or even 15-5 with some no decisions scattered about. But put that guy against a patient lineup that forces him to throw in the zone, and he’s toast. I know because I watched the Giants work Kyle Lohse in the NLCS in 2012. He’d had a good year up to that point, but he hadn’t faced a good situational hitting team like the Giants in their 2010-214 run. The saw him once earlier in the series and tagged him for hits but not a lot of runs. They saw him again in game 7, waited for their pitch, and made better contact and chased him after a few innings.
Thanks all, this has been really illuminating.
Chronos, I did know about walking on 4 balls but I had naively thought that you either walked someone or not, so thanks to you and ashahi for laying out the importance of the count and the ways that pitchers can manipulate the batter by leaving them uncertain about whether to hit or not. This has a parallel in cricket - as mentioned in the OP, bowlers will often bowl slightly wide of the stumps when looking for a catch. Of course, the safe option for the batter is to leave those balls well alone - so the bowler will bowl some that will just hit, rather than just miss, which the batter must play at, if only defensively. The mark of a good bowler is that he can get the batter to play shots he doesn’t have to, and better yet to play and miss. When the batter is swinging at balls he could leave and then not making contact, it’s a sign the bowler is on top of him.
The discussion about the mental aspect of getting in batters’ heads was interesting (the Maddux story may not be true but it should be!). Does the reverse happen? I imagine that if a batter were to demonstrate early in an innings that he can pick the balls from the strikes it would inhibit the pitcher somewhat in later at-bats. This raises another question I had based on the Moneyball book and movie. There’s a lot of discussion about the ability to draw walks and how valuable this is. How do batters do this? As mentioned, a dangerous hitter might be deliberately walked, but the implication in Moneyball is that batters can to some extent manipulate the pitcher to get a walk. Can they somehow force the pitcher to aim for the edge of the strike zone more than they should?
I think that it’s generally difficult for a batter to force walks, other than, of course, intentional walks, and semi-intentional walks. In an intentional walk, the catcher would come out of his stance, and the pitcher would clearly throw four balls, well out of the strike zone (note that, in MLB, they changed the rule last season, and the manager of the team in the field now simply informs the umpire that the batter is being walked). In an “semi-intentional walk,” the pitcher is pitching traditionally, but not really trying to throw strikes – if he’s able to get the batter to swing at a bad pitch, great, but otherwise, he’s willing to concede the walk. When this is done, it’s nearly always against a dangerous hitter.
I think that what Moneyball is referring to is the value of batters who show patience at the plate, and don’t often swing at pitches that are outside the strike zone. Such a batter is going to draw more walks than a “free swinger,” who’ll swing at just about anything. As I remember it, one of the concepts in Moneyball (particularly the film) was that baseball traditionalists were underestimating the value of a walk, as compared to a hit, and the A’s were going against the grain, by actively selecting players who frequently drew walks. (Note, of course, that a walk is not always as good as a hit, as a walk is only for one base, and only advances runners who are forced, and only by a single base, but that’s another conversation. )
As a corellary, a batter who becomes known for having a good eye at the plate, and who doesn’t swing at balls, may actually be more likely to get good pitches to hit, as pitchers realize that they’ll need to throw strikes to get that batter out.
Another side note about terminology, here: A “hit” does not mean “the bat made contact with the ball”, as you might think. If the batter makes contact, but the ball goes foul (outside of the quadrant defined by the lines from home to first base and home to third base), or is caught before it hits the ground for an out, or both (foul balls can be legitimately caught for an out), then it’s not counted as a “hit” in the official statistics. So a “hit” is almost never worse than a walk, but a walk is, on average, better than a situation where the bat and ball make contact, because a lot of those situations have no or negative effect.
Plus, to some degree, if a batter is well known for having a good eye (i.e. never swings at balls outside the strike zone), umpires may tend to call more balls than strikes on pitches right on the edge of the strike zone, thinking that if the good batter didn’t swing, it’s more likely to be out of the strikes zone.
Not a huge effect, hopefully, and likely a lot smaller now than in the past before MLB had good data on how accurate individual umpires are, and used it to help umpires improve.
There’s a story from the Twenties that, with the great Rogers Hornsby at bat, the umpire responded to a complaining pitcher “Young man, when you throw a strike, Mr. Hornsby will let you know.”