NEW YORK -- Through the first 87 games of this season, you could count the Yankees' bright spots on the fingers of one hand and still have two fingers left over: Masahiro Tanaka. Dellin Betances. And most games, Brett Gardner.

And in the 38 games since, you can add another: Brandon McCarthy.

Unfortunately for the Yankees, McCarthy arrived here just as Tanaka was leaving for an extended absence -- McCarthy was acquired July 6, and Tanaka went down with an elbow injury two days later -- so the Yankees didn't add a bright spot; they merely substituted one for another.

But throughout his brief tenure in pinstripes, McCarthy has filled the void left behind by Tanaka's injury: that of ace. For the past six weeks, no Yankees starter has pitched better than McCarthy. None has pitched even nearly as well, although Shane Greene has had his moments.

But in eight starts for the Yankees, McCarthy has been unparalleled. With the Yankees he is 5-2 with a 1.90 ERA, which is not bad work for anyone, but it's especially good for a guy who came over from the Arizona Diamondbacks with a 3-10 record and 5.01 ERA. He was a pitcher his former team had given up on, a player his former organization considered to be worth no more than Vidal Nuno, about whom the Yankees pretty much felt the same way.

Now, after McCarthy's masterful shutout against the Houston Astros on Thursday -- a four-hit, eight-strikeout, no-walk, 107-pitch and 127-minute gem -- it seemed perfectly natural for someone to throw around the "A" word (as in ace) when asking Joe Girardi about him, and just as natural for the manager to agree.

"He really has [been]," Girardi said. "He’s been really, really good from his first start all the way through. He’s given us distance. He’s gone deep into games, and they’ve all been quality starts."

Now, either GM Brian Cashman and his staff are geniuses of the stature employed by MIT or someone in the Diamondbacks' office made a huge mistake on this one, because McCarthy hasn't looked anything like the pitcher one might have expected the Yankees to be getting when the trade was made. At the time, this looked like a classic change-of-scenery swap, in which two teams unload guys they have given up on, each hoping the other was wrong.

Nuno has struggled, going 0-3, albeit with a 3.72 ERA, in eight starts for the D-backs. McCarthy, meanwhile, has flourished against all odds in the Bronx.

"We knew he was a better pitcher than his numbers indicated," Girardi said. "We’d seen it firsthand. We knew he had the ability to pitch, we knew he had a good fastball, a good cutter, a good curveball, so it’s really worked out, and he’s thrown the ball great for us."

It hardly seemed likely when McCarthy came over, having allowed 15 home runs in 109 1/3 innings as a Diamondback and coming over as a right-hander to a homer-friendly park with a short right-field porch in a hitting-happy league.

Yet somehow, McCarthy has transformed in six short weeks into a strike-throwing machine. On Thursday, 79 of his 107 pitches were strikes, and he went to just one three-ball count all game, to Chris Carter, an eventual strikeout victim, in the fourth. Most importantly, he has kept the ball in the ballpark; as a Yankee, McCarthy has allowed just three home runs in 52 innings, two of them at Yankee Stadium.

"I think my pitch mix is better now," McCarthy said. "The cutter and the four-seam have become pitches I can use as weapons again. In turn, that just starts to build confidence. Kind of becomes a self-fulfilling thing. In Arizona, I wasn't getting out of jams and not performing well. That starts to roll. Here I feel confident again. I feel like I'm able to get through situations I wasn’t there. Then you start to believe you can."

Brandon McCarthy

#38 SP
New York Yankees

2014 STATS

• GM26

• W8

• L12

• BB27

• K144

• ERA4.01

McCarthy downplayed reports that the Diamondbacks had dissuaded him from throwing his cutter, a pitch the Yankees encouraged, and got some unexpected help from Francisco Cervelli, who delivered a rather loud seventh-inning pep talk when he sensed McCarthy was beginning to lose his focus.

"He was angry with me," McCarthy said. "He was like, 'Your stuff's so good, let's go. We’re going to get all the way through this.' From early on in the game, he was on me. And then when I was lulling a little bit, he made sure to stay on top of me. He was yelling at me more than anything, which was that nice little kick in the ass that I needed."

Not that he needed much. McCarthy got into two jams all game: in the fourth inning, when Robbie Grossman's leadoff single broke up a no-hitter and Dexter Fowler's broken-bat double gave the Stros runners at second and third with two outs, and again in the seventh, when a single and a double gave them runners at second and third with one out.

McCarthy escaped the first jam by getting Marc Krauss on a comebacker that smacked off his leg, although there was an anxious moment when he couldn't find the baseball. And he was helped in the second one when Krauss' liner into the right-field corner bounced into the seats, forcing Fowler to stop at third. But he took care of the rest by striking out Jon Singleton with a 94 mph fastball and getting Carlos Corporan to fly out weakly to left.

"It's nice when you’re able to go deeper in the game, take some stress off the bullpen, give those guys a day," McCarthy said. "And then just for myself to be able to get deeper in a game. It’s been a point of pride for me, and something I haven’t been able to do well this year."

Despite a pregame players-only meeting in which Yankees hitters vowed "enough is enough," according to Chase Headley, the offense scored just three runs again. All of them came in the second inning, on a single by Mark Teixeira, back-to-back doubles by Martin Prado and Headley and a sacrifice fly by Ichiro Suzuki. But considering McCarthy has allowed as many as four earned runs in just one start as a Yankee -- in the other seven, he has allowed one three times, two twice and now zero twice -- for once, a slim Yankees lead felt a lot bigger than it actually was.

"He did an amazing job," Cervelli said. "With Mac on the mound we only need a couple of runs. That's it."

That's what catchers say when they're talking about the ace of a pitching staff.

And incredibly, in just six weeks, that is what McCarthy has become for the Yankees.