Seles, who won the U.S. Open in 1991 and 1992, spent more than 175 weeks ranked first and was elected to the International Tennis Hall of Fame in 2009.
She teamed with Chris Evert for a fun-and-games exhibition match against Jason Biggs and Rainn Wilson before Thursday night's main event, the quarterfinal between Novak Djokovic and Mikhail Youzhny.
Seles said being on the main court at the U.S. Open was a thrill.
"It brought back so many memories. You could feel the electricity," she said.