They'll now try to make things tough for Jordan Zimmermann -- who has been susceptible to the long ball lately -- as they go for an eighth straight victory Saturday at Nationals Park.New York has been scoring runs consistently during its recent surge, and it got the better of Gio Gonzalez and the Washington bullpen in a 7-2 victory Friday to end the Nationals' six-game winning streak. Curtis Granderson drove in three runs for the Yankees, who have won 17 of 21 to open a 1 1/2-game lead over second-place Baltimore in the AL East.The Nationals (38-24) are atop the NL East largely due to a staff that owns a major league-best 3.01 ERA, but they conceded their most runs since May 13 on Friday."We knew that they were playing really well," winning pitcher Phil Hughes said. "Thankfully, we scored some runs."The Yankees (38-25) have been doing plenty of that lately, reaching the six-run mark in half of their last 20 contests. They were on the verge of winning a game without homering for the first time all season until Granderson, batting .360 with three home runs during a six-game hitting streak, hit his 20th in the ninth inning Friday.New York leads the majors with 97 home runs, and Zimmermann (3-5, 2.91 ERA) has surrendered eight homers in his last five starts.Against Boston on Sunday, Zimmermann allowed David Ortiz's solo shot and two other runs while striking out seven in seven innings of Washington's 4-3 win, although he didn't get the decision. Having yielded three runs or fewer in nine of his 12 starts, the right-hander easily could have a few more victories, but his run support average of 3.26 ranks among the worst in the majors.Washington could again have trouble offensively Saturday with the Yankees giving the ball to Andy Pettitte (3-2, 2.81).Pettitte, who turned 40 on Friday, has pitched at least six innings in each of his six starts and is fooling batters at a surprising rate, striking out 40 in 41 2/3 innings. His ratio of 8.6 strikeouts per nine innings is nearly two above his 17-year career average."People ask me about all the strikeouts, and I can't explain it," he told the Yankees' official website. "I'm just going to roll with it."Pettitte is also holding left-handed hitters to a .178 average, but that is unlikely to intimidate rookie sensation Bryce Harper, who is hitting .383 off lefties.Pettitte gave the Yankees a bit of a scare against the New York Mets on Sunday, when he snared Scott Hairston's sixth-inning comebacker with his bare hand. He finished the inning before exiting, and ended up allowing three runs and five hits while striking out eight in a 5-4 comeback win.X-rays were negative and he reported no problems during a bullpen session Wednesday.Pettitte is 3-1 with a 4.29 ERA in six career starts against the Washington franchise, with his last outing coming in 2006 -- two years before Nationals Park opened.This will be Zimmermann's first start against the Yankees, but he has proven to be quite confident pitching against the AL. His 1.82 ERA in nine interleague starts since 2009 is the fifth-best in the majors in that span among those with at least 50 innings pitched.