With his fifth inning strikeout of Justin Morneau on Monday night, Andy Pettitte became the Yankees' all-time leader in strikeouts. With 1,958 whiffs as a member of the Yankees, Pettitte surpassed Whitey Ford's long-standing franchise mark.
Overall, Pettitte now has 2,386 strikeouts, but 428 of those came as a member of the Astros.
Ford, who was inducted into the Hall of Fame in 1974, is still the franchise leader in wins with 236. Pettitte has 213 as a Yankee (good for third, behind Ford and Red Ruffing's 231 wins) and 250 overall.
As for greatest Yankee pitcher of all-time, the discussion is essentially down to Ford and Pettitte's teammate Mariano Rivera, who's in his final season.
Although a good starter is typically more valuable than even a great reliever by virtue of the vastly greater innings load, Rivera's excellence is such that we have a certifiable debate. While WAR is by no means a discussion-ender, it's worth noting that, according to Baseball-Reference, Rivera narrowly leads Ford on the all-time Yankee pitching WAR leaderboard.
Pettitte, for what it's worth, ranks third on that list, just ahead of Ron Guidry.