The pitcher, hitter and catcher intersect at the borders of the strike zone. Any one of the three can decide the course of an at-bat by commanding the edges.
For the pitcher, a strike on the black is the most difficult for the batter to handle. On the other hand, if the batter can hit or foul off an offering just inside the zone, or lay off one just outside it, it spoils a pitch. And the catcher framing a borderline pitch can be the difference between a strikeout and a walk, or at least a pitcher's count vs. a hitter's count.
It all starts with the pitcher. The first step, after all, is to get the ball to the edge, before the hitter can react to it or the catcher can present it to the umpire.
Thanks to Statcast™, we can see which pitchers are the most precise painters. Statcast™ tracks the location of every pitch across the Major Leagues, mapping it with a detailed strike-zone grid. Any pitch that crosses the plate within one baseball's width of the edges of the strike zone is classified as borderline.
Let's take a look at the starting pitchers who lived on the edges in 2017:
Highest edge percentage by a starting pitcher in 2017
Minimum 2,000 total pitches thrown

1. Dallas Keuchel, Astros: 43.0 percent
   
2. Kyle Hendricks, Cubs: 42.6 percent
   
3. Bartolo Colon, Braves/Twins: 42.1 percent
   
4. (tie) Michael Wacha, Cardinals: 41.7 percent
   
5. (tie) Jason Vargas, Royals: 41.7 percent
   MLB average: 38.8 percent
   Who pitched to the edges most often last season? The top of the list is no surprise, featuring some of the game's best-known command artists. Keuchel, especially, never gives in, staying away from the heart of the zone with every pitch in his repertoire. The southpaw's pinpoint location makes him extremely tough to square up, despite a fastball that averages below 90 mph. Ditto for Hendricks, who has the reputation of being one of MLB's smartest pitchers. And then there's the crafty veteran Colon, whose production declined in 2017. But he still made 28 starts in his age-43 season, while throwing more than 80 percent fastballs and nearly 60 percent two-seamers -- a pitch he loves to run back onto the edges of the plate.

Highest called-strike rate on borderline pitches taken from a starting pitcher in 2017
Minimum 400 borderline pitches taken by hitters

1. Colon, Braves/Twins: 59.9 percent
   
2. Julio Teheran, Braves: 59.6 percent
   
3. Keuchel, Astros: 55.6 percent
   
4. Zack Greinke, D-backs: 55.2% percent
   
5. Zach Davies, Brewers: 54.4 percent
   MLB average: 46.9 percent
   The thing is, though, borderline pitches don't always go the pitcher's way. (This makes sense, because the "borderline" classification includes pitches just off the plate.) In fact, in 2017, below half of borderline pitches thrown by starters and taken by hitters were called strikes. But some pitchers got the call more often. Pitchers like Colon, Keuchel and Greinke have longstanding (and well-earned) reputations as players who can spot up their pitches, and they got called strikes on edge pitches at some of the highest rates in the Majors last year.
   Framing is also likely at play here. The presence of Colon's previous Atlanta teammate Teheran at No. 2 lends support to that -- their catcher, Tyler Flowers, had the highest called-strike percentage of any regular backstop in 2017. So does Greinke's ranking at No. 4, as Arizona catcher Jeff Mathis had the third-highest called-strike rate. Greinke's called-strike rate on borderline takes increased several percentage points from '16, when D-backs catchers notably struggled with framing.

Highest whiff-per-swing rate on edge pitches by a starting pitcher in 2017
Minimum 400 borderline pitches swung at

1. Corey Kluber, Indians: 38.1 percent
   
2. Robbie Ray, D-backs: 36.6 percent
   
3. Chris Sale, Red Sox: 36.2 percent
   
4. Yu Darvish, Rangers/Dodgers: 34.5 percent
   
5. Jacob deGrom, Mets: 34.2 percent
   MLB average: 24.5 percent
   These are some of MLB's premier strikeout artists, and when this group threw borderline pitches in 2017, hitters missed on more than one out of every three swings. Naturally, their whiff rates on edge pitches were all higher than their general whiff rates for the year, and much higher than their whiff rates on pitches within the interior of the strike zone. Darvish drew the biggest whiff-rate boost from pitching on the edges, coming in 6.3 percent better than his overall season rate of 28.2 percent. Kluber had the biggest difference between edge-whiff rate and interior-zone whiff rate -- inside the borders, he got whiffs on 15 percent of swings, a gap of 23.1 percent.
   It's interesting to look at which borders, and pitch types, produced the most swings-and-misses for these pitchers. For Kluber, the majority came on the low-outside corner (to a right-handed hitter), with his curveball and cutter. Ray got whiffs across the top edge of the zone with his four-seamer, and on the low-inside corner with his curve and slider. Sale's three-pitch mix got swinging strikes around the zone -- his fastball at the top edge, his slider on the low-inside corner and his changeup on the lower and outer edges. Darvish would burn his fastball by hitters up-and-in, and make them wave at sliders and cutters low-and-away. And deGrom worked the top and outside edges of the strike zone with his four-seamer, the low-outside corner with his slider and curveball and the low-inside corner with his changeup.

Most strikeouts on edge pitches by a starting pitcher in 2017

1. Sale, Red Sox: 142 (of 308 strikeouts overall)
   
2. Kluber, Indians: 139 (of 265 strikeouts overall)
   
3. (tie) deGrom, Mets: 120 (of 239 strikeouts overall)
   
4. (tie) Max Scherzer, Nationals: 120 (of 268 strikeouts overall)
   
5. Chris Archer, Rays: 115 (of 249 strikeouts overall)
   The top five of this list were the overall strikeout leaders in the Majors in 2017, but it's still worth noting who put away the most hitters with pitches on the edges, especially because the order isn't quite the same. Sale stays at the top, but Kluber jumps to second over Scherzer, notching 19 more strikeouts on the edges, even though Mad Max struck out more batters overall. deGrom also moves up, tied with Scherzer and ahead of Archer in edge strikeouts, despite having 29 fewer K's than Scherzer and 10 fewer than Archer.

Lowest expected wOBA allowed on edge pitches by a starting pitcher in 2017
Minimum 200 at-bats decided on edge pitches

1. Sale, Red Sox: .188
   
2. (tie) Scherzer, Nationals: .196
   
3. (tie) Kluber, Indians: .196
   
4. Stephen Strasburg, Nationals: .208
   
5. (tie) Chase Anderson, Brewers: .209
   
6. (tie) Clayton Kershaw, Dodgers: .209
   MLB average: .268
   These are the pitchers who were most dominant when they hit the edges in 2017. Expected wOBA gives an overall measure of how well a pitcher performed, based on quality of contact allowed, walks and strikeouts. This is a who's who of the biggest names in pitching, with the addition of Anderson, who had a breakout season for Milwaukee and ranked highly in both borderline and overall xwOBA. (Anderson's .273 xwOBA for the season was ninth lowest among pitchers who pitched at least 500 at-bats.) All lights-out pitchers last season, Sale, Scherzer, Kluber, Strasburg, Anderson and Kershaw were even more so in at-bats decided on pitches on the edges of the strike zone.