Since Willie Randolph and Rick Peterson were fired as manager and pitching coach of the Mets on June 17, the team has an 11-2 record in the six games started by Oliver Perez and the seven started by Mike Pelfrey, two starters in whose games the team had gone 11-16 before the infamous firing. Not coincidentally, the Mets, who were 34-36 and 6.5 games out at the time of the midnight massacre, are now 57-48, a game up on the second-place Phillies after Johan Santana demonstrated yesterday yet again that he is, in fact, as good as advertised. That’s baseball; two jokers turn into aces and a team thrives. Randolph and Peterson are doubtless gritting their teeth at the whole spectacle.

This isn’t, of course, happenstance. The team has been winning more when these two start because they’ve been pitching a lot better. Perez’s ERA has dropped by more than two runs since Jerry Manuel was appointed manager and Dan Warthen pitching coach, and he’s walking half as many batters. Pelfrey’s ERA has been more than halved, from 4.62 to 2.12, while his strikeout rate has increased by half and his walk rate has dropped by a third. Both, basically, have gone from pitching like random chumps to pitching like no. 1 starters, and with the pair scheduled to pitch crucial games against Florida tomorrow and Wednesday, the question is really whether they can keep it up.

Another way of putting the question is to ask whether they’ve really been pitching differently during the last month than they had before. If so, their improvement under Warthen is probably sustainable, based on new approaches to getting hitters out; if not, it probably isn’t and may be more a matter of random variance than anything else. Fortunately, this question is easier to answer than it ever has been, thanks to MLB.com’s systematic charting of pitches for online broadcast. The velocity, break, spin, and location of every pitch is recorded and stored, and several incredibly clever bloggers have devised ways to make this information usable. Check brooksbaseball.net, for instance, and you can chart each pitch Perez and Pelfrey have thrown since new management came in against those they threw before. The results are surprising.

In Perez’s case, his improved results are the result of what everyone has seen: He’s been throwing more and better strikes. The former is obvious from his results and his walk rate; in Pelfrey’s case, we need to look at the data on a more granular level. Brooksbaseball, for instance, charts the mean distance of each pitch from either edge of a neutrally defined strike zone. In the six starts before Peterson and Randolph were fired, the average Perez fastball came in 2.18 inches away from the edge of the zone; in the six since, they’ve come in 1.8 away. That may not sound like an enormous difference, but the cliche about baseball being a game of inches is literally true. The difference between 2.18 and 1.8 is nearly 25%, and it’s tracked with the enormous decline in Perez’s walk rate.

For Pelfrey, the difference is more dramatic. According the algorithm by which MLB.com classifies pitches — which isn’t wholly reliable — he didn’t throw a single pitch that classed as a true curveball in the seven starts preceding the firings. Since then, he’s thrown five a game, and occasionally a few more, while more than halving the use of pitches that broke like sliders, essentially abandoning his weak changeup, and greatly increasing his use of straight fastballs. Interestingly, his average fastball is no closer or farther from the edge of the zone; the only real differences are in the slightly altered mix of his secondary pitches and in when he’s throwing them. But they’ve made all the difference between a frustrating fifth starter and a pitcher who’s thrown seven or more innings while allowing one or no runs in four of five starts.

The dime version of the story is that Perez is the same eclectic pitcher he’s been for years — sometimes he throws huge sweeping breaking balls, sometimes tight ones; sometimes he throws sidearm, and sometimes he doesn’t — but he’s actually been throwing strikes of late, whatever the mix of pitches and angles, while Pelfrey has been pitching no more nor less aggressively than usual, but with a somewhat altered arsenal. However much you want to credit the new regime for this, both men are doing something qualitatively different from what they were doing under the old one, which augurs well for the Mets. What they were doing wasn’t working, and they aren’t doing it anymore; what they are doing is working, and there’s no reason to think they can’t keep at it. Perez may be genetically incapable of actually keeping the ball near the plate, and Pelfrey of mixing his pitches, but you’d have a hard time proving it by what they’ve done for more than a month now.

tmarchman@nysun.com