Cashner

Red Sox starter Andrew Cashner delivers a pitch during the first inning against the New York Yankees Friday night at Fenway Park.

Then covering baseball for the Philadelphia Inquirer, John Lowe invented a baseball statistic in 1985 and it caught on. Lowe defined a “quality start” as any in which the starting pitcher lasted six innings or more and surrendered three or fewer earned runs.

At the time, it seemed like such a ridiculously low standard, particularly the innings minimum. After all, Lowe’s definition came only 32 years after Robin Roberts threw 28 consecutive complete games for the Phillies, and just 13 seasons after Cardinals great Bob Gibson, sadly now suffering from pancreatic cancer, completed a five-season stretch in which he logged 125 complete games. That’s an average of 25 CGs per year, math fans.

Six innings doesn’t seem low anymore. Lowe was way ahead of his time. The game has caught up to him with a fury. The terms of the statistic fit the definition of quality in today’s game. Pitchers have it tough. The baseball is juiced and so are a high percentage of the hitters, although in ways that aren’t as easily detectable by testing as when steroid suspensions were happening. Video is so detailed now that hitters can familiarize themselves with the nuance of every pitcher’s pitch. Managers are armed with more data to take advantage of matchups.

The hitters have outgrown the ballparks, so pitchers need to work the edges of the strike zone more frequently and as a result tend to run high pitch counts.

So six innings and three runs is in fact a quality start in every sense of the term. Those were Rick Porcello’s numbers in Thursday night’s 19-3 rout of the Yankees in the opener of a four-game series at Fenway Park. And that’s all the Red Sox need from the 2016 Cy Young Award winner as well as from the four starters who join him in the rotation.

And finally, that’s what the starters have been giving them against quality competition of late.

Porcello’s start completed a full turn in the rotation in which each pitcher lasted at least six innings, the last four fitting the definition of quality start. No. 5 starter Andrew Cashner, who made his third start for the Red Sox on Friday night against the Yankees, was the only pitcher who did not get credit for a quality start because he gave up four runs in his six innings. Eduardo Rodriguez, on quite a roll, followed that with seven shutout innings. In his second consecutive encouraging start, Chris Sale allowed two runs in six innings. Then David Price allowed three in six innings in a losing effort.

“It starts with those guys on the mound, and this is the fifth one (in a row) that we go six-plus,” Sox manager Alex Cora said after his team’s second victory in eight games against the Yankees this season. “That’s great. Those guys do what they usually do and they’re going to put us in a good spot. We know we’re going to score runs.”

The rotation has been better than the bullpen, but not in terms of meeting expectations. Those were high for the starters, low for the relievers. Even if the bullpen doesn’t come around, if this mini-run from the rotation continues, it’ll be tough to keep the Sox out of the playoffs, given the potency of the top of the order. It starts with reigning American League MVP Mookie Betts and continues with bona fide MVP candidates Rafael Devers and Xander Bogaerts. All three are on fire.

“It’s been absolutely incredible,” a grateful Porcello said of the offense. “It seems like the last three or four games I’ve pitched we’ve scored damn near 20 runs. It’s huge. When we’re scoring like this, you do the best you can to not screw it up.”

Porcello (9-7, 5.55) was credited with the win in each of his past four starts, although he didn’t pitch very well in two of them. The Red Sox run totals in the four games: 7, 10, 16, 19.

“The way our offense is swinging the bats, as long as we can go out there as starting pitchers, keep us in the game, give us a chance to win, we’re going to be in good shape,” said Porcello, who retired Aaron Judge on a fly to center to leave the bases loaded in the Yankees’ two-run second. The slider was a big pitch and proved his head was in the right place, thinking about the next pitch. He had gotten ahead of Judge, 1-2, only to not get the call on the next two borderline pitches.

“He was able to give us six,” Cora said. “It was a good night for him.”