The accident happened fewer than four months after another spectator was killed in a similar fall.
The fan, a 26-year-old man, fell about 10 p.m. from the box-seat level to a floor near Gate D at the stadium as the Mets played the St. Louis Cardinals, police Detective Brian Sessa said.
The unconscious man was taken to a hospital, the Fire Department said. He was in critical condition early Sunday but expected to survive, said police Lt. John Grimpel.
As the game continued in extra innings, the team issued a statement saying it was aware of the fall and was investigating.
On April 15, fan Antonio Nararainsami, 36, lost his balance on an escalator and fell two stories to his death in a section below the left field stands. Nararainsami was leaving the stadium with his family after the Mets played the Washington Nationals.
The stadium's escalators were also the scene of a fatal fall in 1985, when a 21-year-old Yonkers man fell 100 feet.
This is the Mets' last season at Shea Stadium. A new stadium, Citi Field, is scheduled to open next year.
Crane accident at Cowboys’ stadium site injures 3
Mets will not start Pedro vs. Phillies next week
