NEW YORK -- Presented with a second chance to give the San Francisco Giants an extra-inning lead Saturday, Mac Williamson treated it like a pitch down the middle. He wouldn't let it pass him by.
Williamson drove in both Giants runs, including the go-ahead tally with a 12th-inning single that hastened San Francisco's 2-1 victory over the New York Yankees. The decision ended the Giants' season-high, six game losing streak and kept them four games ahead of second-place Los Angeles in the National League West.
Williamson broke a 1-1 tie in the 12th with a one-out hit that scored Trevor Brown, who doubled to lead off the inning against Anthony Swarzak (1-1). Two innings earlier, Williamson struck out against Aroldis Chapman, the Yankees' dominant left-hander, with Grant Green on second base and nobody out.
Self-critical over his inability to accomplish anything in the 10th -- "I couldn't get [Green] over; I couldn't get him in," Williamson said -- he connected with Swarzak's 1-0 delivery and grounded it sharply into center field past diving Yankees shortstop Didi Gregorius.
"I was trying to drive something up the middle of the field, and not get too pull-happy, to give Trevor an opportunity to score," said Williamson, who also homered in the fifth inning. "He left a slider over the middle of the plate and I snuck it by Didi a little bit, just enough."
• Williamson gets redemption with two big hits
The Yankees, who fell to 4 1/2 games back of the second American League Wild Card spot, mustered three hits in the final eight innings against Giants starter Johnny Cueto and six relievers. Yankees starter Ivan Nova sparkled, allowing one run and six hits while striking out seven in seven innings. But he was matched by Cueto, who surrendered an unearned run and six hits while striking out nine in six innings.

MOMENTS THAT MATTERED
Fit for flip-flop: Cueto, who felt weakened and reported pain in his left side after his last start, looked strong against the Yankees, striking out nine in his six-inning stint. Knowing he soon would switch places with Jeff Samardzija, the Giants' No. 2 starter coming out of the All-Star break who occupied the No. 3 spot during the season's first half, Cueto responded well.
"I felt 100 percent better," said Cueto, who was weakened by a virus and discomfort in his left side when he faced San Diego last Sunday.

Blown opportunities: The Yankees struggled with runners in scoring position all night, but nowhere was this more apparent than in the bottom of the 10th inning when, after loading the bases with three walks, neither Brian McCann nor Castro could drive in a run. In all, the Yankees finished the day 0-for-10 with runners in scoring position and stranded 10 baserunners.
"It hurts," Yankees manager Joe Girardi said. "We had the opportunity to score some runs and we weren't able to do it. To lose a game 2-1 in 12 innings is really difficult." More »

Sweet relief: The Giants, Bochy said, still struggled to produce the timely hit, but this time their staff put a chokehold on the Yankees offense until they could get it. After Cueto battled through his six innings, the San Francisco bullpen pitched six scoreless frames.
Closer Santiago Casilla, who hadn't pitched in a week since blowing his first save opportunity after the All-Star break, pitched a scoreless 10th and 11th to pick up the win -- all while dealing with rumors that the Giants are seeking relief help, possibly someone to compete for his job, as the Aug. 1 non-waiver Trade Deadline looms.
"Well, of course I've thought about it, and of course it would bother me," Casilla said through a translator. "I've been doing the job. I have a lot of experience during the regular season, the playoffs. I have three World Series rings, and I have shown that I can do the job."
McCann doesn't look back: With one out in the bottom of the eighth inning and the game still tied, McCann stood on first base with Castro at the plate. Castro blooped a popup into left field and McCann ran on contact, making it halfway to third base before he realized Ángel Pagán had caught the ball. Pagan softly lofted the ball to Brandon Belt at first, doubling off McCann and ending the Yankees' modest threat.
"I [thought it would get down]," McCann said. "I was trying to get to third base and I thought it was going to get down before he got there."

QUOTABLE
"Obviously we're not going to win every game. As hard as we play, we're going to lose some. We have a lot of games left, but I feel like we've been playing better ball and we've got to just continue to do that." -- Yankees reliever Dellin Betances on the do-or-die perceptions surrounding the Yankees' season
WHAT'S NEXT
Giants: Samardzija will try to improve upon his previous start against the Yankees when he faces them in Sunday's series finale beginning at 10:05 a.m. PT. Samardzija yielded nine runs to New York in 4 2/3 innings last Aug. 2 while pitching for the White Sox.
Yankees: The Yankees will send Nathan Eovaldi to the mound Sunday at 1:05 p.m. ET, making his second start since returning to the rotation after a brief stint in the bullpen before the All-Star break. Eovaldi has had no answer for the Giants in his career; his 13.30 ERA is his worst mark versus any team against whom he's thrown at least one inning.
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