NEW YORK – Who is this Pedro Ciriaco? How is it possible that he’s doing this to the Yankees? How did he get to the Red Sox? And how did Robinson Cano help to turn him into the scourge of New York?

Such is the nature of the kind of out-of-nowhere revelation offered by a previously unheralded players such as Ciriaco who suddenly finds himself amidst a run with little precedent. On Saturday, the shortstop went 4-for-4 with a single to right, a single to left, a bunt single to third and a double to left.

In its own right, the day was impressive enough. Taken in broader context, it continued an astonishing run. Ciriaco is now 15-for-29 (.517) against the Yankees this year. He has the highest batting average ever against New York by a player with at least 25 plate appearances against the Yankees, exceeding the .462 mark that Glenn “Mother” Hubbard enjoyed in his career. He became the first Red Sox since Wade Boggs in 1989 to have two four-hit games against the Yankees in the same season, and of his six three-hit games with the Red Sox, four have come against New York.

“He's gotten us all year long,” lamented Yankees manager Joe Girardi after Ciriaco helped the Sox claim a 4-1 win at Yankee Stadium. “I mean, it's unbelievable.”

In the visitor’s clubhouse, Bobby Valentine bordered on giddy in discussing the rail-thin 26-year-old.

“You think [the Yankees are] going to try to trade for him if he clears waivers? He's played well against them,” said Valentine. “Doesn't surprise me -- it amazes me that he is who he is with that kind of talent and hasn't been utilized before."

So how did Ciriaco get to this point?

He was a toolsy middle infielder when the Diamondbacks signed him out of the Dominican as a 17-year-old in 2003. His glove and speed were both obvious tools, but his offense lagged, as his wiry frame supported little power potential and he was a free-swinger with poor OBPs.

Still, given his glove and speed, he played his way onto the 40-man roster in 2009 and then, after a trade to the Pirates in 2010, made numerous trips between Triple-A and the Pirates rosters.

In 2011, the result of that shuffle was limited playing time that had the potential to hinder Ciriaco’s development. He hit .303/.324/.424/.728 as a bench player in 23 big league games, but he would languish for long periods.

“I was back and forth, in Triple-A, then back in the majors, like six times last year,” said Ciriaco. “In the big leagues, about a month, I had just six at-bats. That’s hard. Baseball is hard even when you play everyday. When you play once a week, it’s harder. It’s difficult.”

The numbers Ciriaco posted at age 25 in Triple-A were poor. He hit .231/.243/.300/.543, and with no options remaining, he became a non-tender candidate.

But the Sox had scouted him extensively, liked his defensive and baserunning tools and thought that his stats didn’t accurately represent his offensive approach. And so, the team thought that it had an opportunity to scoop him up on the cheap.

“Pedro Ciriaco is a guy we’ve always liked from a scouting perspective, especially the defense, the baserunning, the ability to do little things. We felt like his bat was developing a little bit late,” explained Red Sox director of pro scouting Jared Porter. “He didn’t get a lot of at-bats in 2011, but in those at-bats, we did feel that he was showing some improvements.”

After the season, the Pirates did not tender him a contract for 2012, thus making him a minor league free agent. 

“Once the non-tender list came out, [Red Sox GM} Ben Cherington actually highlighted him as a guy we should potentially look into signing,” said Porter. “At that point, the pro scouting department took over the signing, but Ben was the guy who put Pedro’s name on the radar.”

As luck had it, it was at that time that Ciriaco -- with an important assist from Cano -- was working to advance his game.

Like Ciriaco, Cano hails from San Pedro De Macoris in the Dominican. Though Cano is three years older than the Red Sox infielder, the two became acquainted this offseason, and Ciriaco was sure to take notes.

“We have a hitting coach and worked together a little bit in the offseason. He’s an unbelievable hitter. [He taught me] to just stay back. That’s what I’ve been doing, stay back and trust my hands,” said Ciriaco. “Just watching how he hits, I can learn about that. I watched him hit and he works hard. Watching him, I learned.

“I worked very hard in the offseason to have success this year,” he added. “I think this year, I’m more consistent. I think I have a little more patience to get my pitch to hit. It’s easier to be more consistent and to have a little more fun.”

Ciriaco was able to apply some of that to winter ball, where he played well. He received interest from the Sox, Marlins and Royals, but Ciriaco was impressed by the Sox organization and liked his opportunity there.

“I just felt like I wanted to play here, wanted to be part of the team,” said Ciriaco.

He agreed to a minor league deal – an essential component of the deal for the Sox, given that Ciriaco was out of options and the Sox wanted him to play everyday in order to cement his improved approach in the minors – that would pay him a major league salary of $500,000, little more than the minimum.

And then, Ciriaco came into spring training and started to open eyes. He managed to contribute in just about every way imaginable, In 26 games, he hit .419/.444/.651/.1.096 with a homer, seven doubles and eight steals while bouncing between numerous positions. The performance was astonishing.

He then went to Pawtucket and enjoyed the best offensive stretch of his minor league career, hitting .301/.318/.406/.724 while playing short and second. Because he was out of options, the Sox wanted to wait until a prolonged opportunity to play arrived before calling him up, and that is precisely what happened in July when Dustin Pedroia was sidelined by a thumb injury.

Ciriaco made his Red Sox debut by going 0-for-4 against the Yankees on July 7, but since then, he’s tormented New York, delivering game-winning hits on consecutive days last month. He’s enjoyed steady playing time, as his performance has mandated a steady if not everyday place in the lineup, whether at second, third or short.

The stretch represented anything beyond what Ciriaco could have fathomed when he signed with the Sox.

“Every time I have a chance to play, I’ve got to take advantage of that, every opportunity here. I try to do my best every time,” said Ciriaco. “[This is] probably something I never imagined. When I got a chance to come to spring training, I wanted to be part of the team. I worked hard everyday to get better and stay consistent. I feel like right now, it’s part of my dream.

“I'm really happy I've been doing what I'm doing. Like I said, not trying to do too much. Just trying to get my good pitch to hit and take advantage,” he added. “I've been able to be more consistent this year. I hope I can keep doing what I'm doing.”

Of course, it would be a bit much to expect that he will hit .500 against the Yankees forever. Even so, in a season where disappointments have been numerous for the Red Sox, Ciriaco stands out as an unexpected exception.

“When a guy's hot, he's hot,” said Ryan Lavarnway, who spent the first three months of the year with Ciriaco in Pawtucket. “He's putting great swings on the ball. He's real fast, so he puts pressure on the defense.”

But ultimately, the catcher suggested, the answer is fairly straightforward.

“Why is he having success?” Lavarnway mused. “Because he's a good player.”