NEW YORK—While warming up on the Yankee Stadium sidelines before Tuesday's game, Alex Rodriguez paused, looked up at the clear blue sky and the thousands of cheering fans in attendance, turned to Derek Jeter, and invoked a classic line from the 1989 film Field Of Dreams. "Hey, Derek?" Rodriguez said, inhaling deeply to convey a sense of wonderment and gesturing woodenly to the thick, green grass below his feet. "Is this heaven?" According to witnesses, Jeter chuckled mildly and then muttered "Fucking loser" under his breath.