When you think of Tim Lincecum, the first thing you probably think of is great pitching.
Lincecum is probably the best pitcher in the game today.
If you really nitpick, you can find a few faults—he could stand to get more grounders and avoid the barrel of the bat more—but there's no question that Lincecum is great. In fact, his 2.45 ERA significantly underrates Lincecum; the long-haired righty's ERA should be right around 2.00.
Beyond thinking of great pitching, you probably think of Lincecum's twisting delivery, his 89-97 mph fastball, or his huge 12-to-6 curveball.
The delivery is mechanically sound and deceptive, and both the fastball and curve are above-average pitches, and all certainly help him achieve his greatness.
One thing that probably doesn't immediately jump to mind with Lincecum, however, is his changeup.
The changeup was never touted on the level of his fastball and curve, and he didn't even learn it until a year before he was drafted.
Despite all of that, the changeup has served as Lincecum's best pitch.
It's rated as the best changeup in baseball this year, coming in at an astonishing 5.29 runs above average per 100 pitches.
In practical terms, that means every 18 changeups Lincecum throws, he keeps one more run off the scoreboard than an average pitcher.
That's a truly astonishing number. Compare that to his fastball, which is .51 runs above average. That means that Lincecum needs to throw about 200 fastballs to achieve as much run prevention as he does with 18 changeups.
Lincecum's curve comes in at .94 runs above average, and his slider is +.74.
This season, Lincecum has deserved to allow 32.1 runs fewer than average.
Since all of his pitches help prevent runs, that number is very high.
However, 22.2 of those 32.1 runs have come courtesy of the changeup, 6.0 because of the fastball, 3.3 because of the curve, and 0.6 because of the slider.
Lincecum is achieving these incredible results largely because of the changeup.
Does that mean it's his best pitch?
Yes and no.
Yes, the changeup has undoubtedly been Lincecum's most effective pitch, and the best often-thrown pitch in baseball this year.
However, it could be that hitters are so bent on looking for the fastball or curve that the changeup surprises them and gets them out.
It is universally acknowledged as a good pitch in its own right, but it's very possible that a good amount of the success of Lincecum's changeup is due to its reputation as the righty's third-best pitch.
Last year, Lincecum's fourth pitch, his slider, was a whopping 6.66 runs above average for a similar reason.
The lesson here is that while Pitch Type Linear Weights are a great stat, they don't tell the whole story. If Lincecum didn't have a good curveball and hitters looked for the fastball or the changeup, the changeup would likely see worse results.
Each pitch in a pitcher's repertoire plays off his other pitches. Very often, you see hard throwers with questionable off-speed pitches have low fastball effectiveness ratings and high off-speed pitch effectiveness ratings.
Sometimes this means that whoever scouted the pitcher's stuff was wrong, but often it means that hitters key in on the pitcher's best pitch and are thus less prepared for his weaker pitches, which makes the best pitch play down and the weaker pitches play up.
That said, there's no doubt that Tim Lincecum has four plus pitches and uses them all to great effect. If he stays healthy, he's going to be a fun pitcher to watch for a long time, unless you're rooting for the team he's facing.