When it comes to pitchers, what numbers matter? The answer continues to evolve as the tools for watching and comprehending the game change, and as ever-gorier math and ever-more-precise technology are applied to understanding the art of pitching.

There was a time when wins and losses were king. That is no longer the case, particularly in an era when starting pitchers are asked to contribute fewer and fewer innings. Across the board, traditional counting stats that show volume (wins, strikeouts, home runs allowed) have given way to a view of those same statistics on a rate basis (strikeouts per nine innings, walks per nine innings, home runs per nine innings).


Even somewhat more descriptive statistics such as ERA are viewed with skepticism in some corners, given the growing awareness that they at times can reflect as much on a pitcher’s defense (not to mention an official scorer) as on the pitcher’s abilities.

Different numbers tell different stories. There’s no statistic that tells a complete story about a pitcher’s abilities. Nonetheless, it’s interesting to hear from people in the game about the first statistic they examine to start forming a sense of a pitcher’s effectiveness. Here are some of their choices:

WHIP Definition: Walks plus hits allowed per innings pitched. This is easily the most popular statistic among Red Sox uniform personnel.

What it shows: Red Sox manager John Farrell: “Does he throw strikes and does he get hit? You can dig into so many other things, but in a snapshot — you can [be effective in] many different ways. So you don’t strike out a lot of people? Well, you know what? Maybe you’re not giving up a lot of hits.’’

2015 major league average: 1.29.

2015 leaders: Zack Greinke (0.84), Jake Arrieta (0.86), Clayton Kershaw (0.88), Max Scherzer (0.92), Jacob deGrom (0.98).


A rebuttal: Red Sox reliever Junichi Tazawa (through translator C.J. Matsumoto): “I’ve never really thought about it, but to me, [the first statistic to look at] would be ERA, because if a pitcher has an ERA of 0.00, even if he’s giving up hits and bases on balls but getting out of that inning clean, that means something.”

K/BB Definition: Number of strikeouts per walk issued by a pitcher.

What it shows: Red Sox farm director Ben Crockett: “You learn about a guy’s ability to get a swing-and-miss. It regresses as a pitcher moves up levels. And it helps determine how good a pitcher’s stuff is and how often he throws strikes.”

2015 major league average: 2.7.

2015 leaders: Max Scherzer (8.1), Clayton Kershaw (7.2), Chris Sale (6.5), Madison Bumgarner (6.0), Bartolo Colon (5.7).

What if ...

Here's how a baseball card might look with advanced metrics replacing traditional stats.

K/9 Definition: Average number of strikeouts per nine innings.

What it shows: Red Sox director of pro scouting Gus Quattlebaum: “I would look at strikeouts per nine, just to measure deception. It could show both [the quality of stuff or a pitcher’s deception], but I care about the deception.”

2015 major league average: 7.8.

2015 leaders: Chris Sale (11.8), Clayton Kershaw (11.6), Max Scherzer (10.9), Chris Archer (10.7), Carlos Carrasco (10.6).

Z-Contact percentage Definition: Measures the frequency with which swings at pitches in the strike zone result in contact (as opposed to producing a swing-and-miss). A lower percentage signifies pitchers with a greater ability to remain unhittable on pitches in the strike zone.


What it shows: Red Sox director of pitching analysis and development Brian Bannister: “To throw pitches in the strike zone, knowing he’s going to get a strike if he doesn’t swing, or still getting the ability to get a swing-and-miss or some positive batted ball while in the strike zone, it’s fascinating, because only a few pitchers can do it with the best hitters in the world. You see the leaders every year — the Kershaws and the [Koji Ueharas], those guys are extremely deceptive. To me, that’s where I start. Can this guy pitch effectively in the strike zone?”

2015 major league average: 86.7 percent.

2015 leaders: Clayton Kershaw (78.2), Chris Sale (78.2), Max Scherzer (78.9), David Price (81.7), Francisco Liriano (82.3)

QS Definition: Quality start, meaning an outing of six or more innings and three or fewer earned runs.

What it shows: Red Sox catcher Ryan Hanigan: “It just shows for a starting pitcher how often they go out there and keep a team in the game — consistency. ERA can get skewed based on a bad outing or two, but over the course of the season, I think that’s a pretty good barometer of what a guy’s got.”

2015 leaders: Zack Greinke (30), Jake Arrieta (29), Clayton Kershaw (27), Dallas Keuchel (27), John Lackey (26).

A conversation with David Price, Brian Bannister, Alex Speier, and Peter Abraham:

FBv Definition: Average fastball velocity.

What it shows: Red Sox baseball operations senior adviser Bill James: “If I only had one piece of information, average fastball velocity. There are just a lot more effective pitchers who can throw 97 than there are who throw 90. Having said that, that area of information is overrated and overvalued, but it’s still the one most important piece of information you can have.”


2015 major league average: 92.1 miles per hour.

2015 leaders: Yordano Ventura (96.4), Matt Harvey (95.9), Gerrit Cole (95.6), Garrett Richards (95.5), Carlos Martinez (95.3).

NOTA Definition: None of the above. For some, the effort to comprehend a pitcher’s abilities does not begin with numbers — and certainly not a single number. Instead, some insist on starting their examination with a traditional scouting report.

What it shows: Red Sox general manager Mike Hazen: “I don’t look at one stat and say that this is starting to paint the picture of what I think about this guy. I look at the scouting report first. I always look at the statistical stuff, too, but that’s where I start. It defaults to the summary of the scout describing the player and all the things in the summary: Velocity, stuff, delivery, athleticism, arm action, all those things — that’s where I go first.”

Alex Speier can be reached at alex.speier@globe.com. Follow him on twitter at @alexspeier.