Rich Harden pitched yesterday for the first time after his recent bout of food poisoning. Unsurprisingly, he was able to get minor-league hitters out. His velocity was only in the low-90s, but he was unconcerned, saying he was happy with it where it was now, and that velocity wasn’t the most important thing. If he were the Mark DeRosa or Ryan Theriot of pitchers, he’d have used the “pitching, not throwing,” cliche.
He’s right, of course. Just throwing hard doesn’t make you a good pitcher. (See Farnsworth, Kyle). And even without a lot of heat on your fastball you can still get batters out. (See Maddux, Greg) Velocity definitely doesn’t hurt, in general, though:
There’s not a strong correlation between velocity and performance (measured in fielding independent pitching), although all other things being equal, throwing faster is probably better than throwing slower – but not enough that you should sacrifice command or anything else for it.
As for Harden himself, Fangraphs has four years of velocity data for him. Last season was the lowest velocity season he’s had – he averaged 92 mph on his fastball, but put up his second-best FIP–2.95. His only better season was the season where he was throwing his hardest – at 94.4 mph, he put up a 2.90 FIP in 2005. So for Harden, it doesn’t seem to be much about velocity; he’s a good enough pitcher that he can get batters out down a couple of miles. The important thing for him is staying healthy, and I’d rather see him able to go out and throw 100 pitches at 90 mph than 50 at 95.