Andy Pettitte Stats To Watch
Pettitte, who celebrated a birthday on Friday, takes the mound for the first time as a 40-year-old. He is looking for the 244th win of his career, which would move him past Juan Marichal and into sole possession of 53rd place on the all-time list.

Pettitte's bread-and-butter out pitch this season has been the slider/cutter, which he has thrown nearly three-quarters of the time with two strikes. Opponents have a meager .444 OPS in two-strike at-bats ending in a slider or cutter, and are hitless in 19 such at-bats over his last two starts.

He has also transformed into an unlikely strikeout machine this season, fanning a career-best 25 percent of batters faced. Thirty-four of his 40 strikeouts have been with his slider/cutter combo, including all eight of his punchouts in his most recent start against the Mets last weekend.

Pettitte struggled in his lone road start this year at Anaheim last month, giving up five runs in seven innings. But since that poor start, he has allowed two runs with 18 strikeouts in 13⅓ innings over his last two outings.

He did a good job limiting hard contact in those two starts against the Mets and Rays, giving up just one line drive among 27 balls in play. Eight of his nine fly balls were turned into easy outs and he didn't allow a homer.

Pettitte also threw nearly half his pitches in the lower third of the zone or below and found success keeping the ball down. The Mets and Rays were 3-for-24 with 13 strikeouts and six groundouts in at-bats ending in a pitch thrown to that location.

Jordan Zimmermann Stats To Watch
Zimmermann was lights-out to start the season, not allowing more than one run in any of his four April starts. But since then he has allowed at least three runs in five of his last eight starts, during which opponents have a .273 AVG/.313 OBP/.444 SLG line against him.

He has a sterling 2.91 ERA this season but is vulnerable to the long ball, which could be trouble against the Yankees, who have scored more than 50 percent of their runs via home runs. He leads all Nationals pitchers with 10 home runs allowed, including eight over his last five starts.

Zimmermann has never faced the Yankees but has pitched well against the American League in his career, having not surrendered more than three runs in any of his nine interleague starts. His 1.82 ERA is the best interleague ERA among active major league pitchers with at least five interleague starts.

The 19-Year-Old National Phenom
Left-handed hitter Bryce Harper has actually hit lefties (.383 BA) better than righties (.268 BA) in his rookie year. The key for Pettitte is to keep the ball away, just like Clay Rapada did last night when he struck Harper out swinging in the eighth inning.

Nearly 60 percent of the pitches Harper has seen from southpaws this season have been on the outer third of the plate or further outside. Harper has just four hits and 10 strikeouts in 22 at-bats (.182) ending in pitches away, and has missed on nearly one-third of his swings against those offerings.