Once the new Yankee Stadium opened and it became clear the short right field porch was even shorter than it had been at the old ballpark, the Yankees started to build their roster around left-handed pull hitters. I mean, they’d always done that, but there was an increased emphasis for sure. It made complete sense too. You tailor your roster to your ballpark since that’s where you play the majority of your games. Every team does it.
The Yankees sought left-handed pull hitters whenever possible. When they needed a short-term designated hitter, they signed guys like Nick Johnson and Raul Ibanez and Travis Hafner.