This was the sort of performance that the Red Sox needed to see in order to feel confident about their rotation for the postseason.

John Lackey had been amidst a strong run dating to his final start of the first half against the Orioles. In five starts, the big right-hander was 4-0 with a 3.41 ERA and, perhaps more notably, 26 strikeouts and just three walks. But as promising as those results had been, they had to be taken with something of a grain of salt.

Lackey’s strong performances had come against lineups that ranged from middle-of-the-pack to abysmal. He had his way with the Orioles and Mariners, with the Rays and the Royals and the Indians. But he had not faced the sort of relentless offense that lays waste to mediocrity.

The Yankees, of course, posed a different sort of measuring stick, a team that entered Saturday ranked second only to the Red Sox in runs per game. That being the case, Lackey’s bend-but-don’t-break outing in a 10-4 win (recap) qualified as one of the more significant performances for the Sox in the second half.

It was the scenario for which Lackey was signed, but in which – for significant stretches of his Red Sox career – it was unclear if the right-hander could deliver. He faced the dual threat of an elite opposing offense and an elite opposing pitcher in CC Sabathia, who entered the day with a remarkable 1.01 ERA over his prior eight starts.

Lackey’s thoughts on that matchup?

“I’ve been around for a while. I’ve won a few big games in my life,” said Lackey. “I’ve got confidence.”

He pitched as if that were the case, trusting his stuff against the deep Yankees lineup. Lackey was not overpowering, needing 115 pitches to make it through six innings. But he made enough key pitches in pivotal situations to limit the Yankees to three runs on six scattered hits.

Lackey pitched carefully and was mindful about staying away from the middle of the plate, resulting in a pair of walks and a pair of hit batters. But he also kept the Yankees guessing on both location and pitch type, on a day when he featured a fastball that registered as high as 94 mph, along with a slider and cutter that he used to get in against lefties and to pitch away to right-handers.

“I squeezed about 10 innings worth of pitches into six innings,” said Lackey, who improved to 10-8 and saw his ERA decline slightly to 6.14. “They make you grind, a lot like our lineup. Can’t make mistakes. It’s kind of a thin line. You want to throw strikes, but you can’t just throw any sort of strike.”

Though Lackey allowed baserunners in five of his six innings, he minimized potential damage. The Yankees were just 2-for-13 with a walk, two hit batters and four strikeouts with men on base against the Sox starter.

It was not overpowering, but by limiting the rallies, Lackey gave his lineup a chance to assert itself. His most impressive stretch came in the fifth, after the Sox had claimed a 7-2 lead. Lackey allowed the first three batters of the inning to reach, including a run-scoring single, but then smothered the middle of the Yankees lineup. He punched out Curtis Granderson and Mark Teixeira on 93 mph fastballs, then got Robinson Cano to ground out to end the threat.

The result was Lackey’s seventh quality start of the year. He was rewarded for that performance by an offense that managed to plate seven runs against Yankees starter CC Sabathia.

The shape of the game offered a two-fold reminder about the team’s postseason prospects. First, the Red Sox offense is so good that the team will have chances to win games against starters who are considered among the best in the game, so long as it gets serviceable pitching from its own end.

Secondly, Lackey gave perhaps his most convincing evidence to date this year that he is capable of delivering what the Sox will need in the postseason from a No. 3 or 4 starter. Certainly, the pitcher’s teammates harbor confidence in what the right-hander can do in those situations because they know that – after years of being the anchor of playoff-bound Angels pitching staffs – he won’t shrink from a challenge.

“For all that he’s had to deal with, he always goes out and competes. You can count on that day in and day out with him,” said catcher Jason Varitek. “He’s just a competitor.”

But now, he is starting to produce solid results to match his competitive nature. Lackey’s record over his last half-dozen starts is 5-0 with a 3.58 ERA. He is getting swings and misses and attacking the strike zone with an array of pitches in a manner that was nowhere in evidence for much of the first half.

While it would be a mistake to get carried away with a run that has been characterized primarily by effectiveness rather than outright dominance – after all, the right-hander still has the highest ERA (6.14) of any AL pitcher with at least 100 innings – Lackey has nonetheless been pitching well at a time when the Sox look like they will need to rely on him.

With Clay Buchholz potentially done for the year, the Sox have an opening for the role of No. 3 postseason starter. The team acquired Erik Bedard at the trade deadline with that fact in mind. But pedigree and Lackey’s recent performance, other members of the Red Sox insist, suggest that the right-hander could be that pitcher.

“Lack’s gone up against guys like CC for a long time. He’s come out on both ends of it. But one thing you know is that he’s going to bust his ass and give you everything he’s got on that fifth day,” said starter Jon Lester. “I don’t think it’s anything that’s shocking to anyone around here. I don’t know if impressed is the right word. When you use the word impressed, that means you’re surprised.

“We’ve all seen him in this clubhouse pitch like he’s been pitching, and I don’t think anyone is surprised by it,” Lester continued. “It’s big. It gives you that extra depth, especially in a short series. It’s a big thing. Teams that have three starters that can match up against anybody, it takes you a long ways.”

Increasingly, it appears as if Lackey might be able to do just that, even against the sort of opponents that the Sox will have to face in the playoffs.