Historical Significance & Shea Stadium Outfield Geometry
On September 21, 2001, ten days after the September 11 terrorist attacks, 41,235 fans packed Queens' Shea Stadium. Trailing 2-1 in the bottom of the 8th inning with one out and Edgardo Alfonzo on first base, Mike Piazza faced Atlanta reliever Steve Karsay on a 1-1 count. Piazza turned on a 94-mph fastball, sending it 417 feet over the 378-foot right-center wall and past the blue fence into the auxiliary television camera enclosure.
The home run caused a massive +0.49 WPA leap (Win Probability Added), instantly flipping the game from a 67% Atlanta win expectancy to an 82% New York Mets victory probability. Shea Stadium—notorious for deep power alleys (371 ft left-center, 378 ft right-center, and 410 ft dead center) and swirling winds from Flushing Bay—rarely yielded opposite-field home runs of that magnitude under extreme late-inning leverage.