"[Gambacorta] was leaning over, and as he leaned over, his momentum made the mat slide out from underneath him," said witness Joe Piacentino Jr. "That's how this happened. He wasn't reaching for a ball that was being hit."
Paramedics attended to Gambacorta before taking him off the field on a stretcher. There was no official word on his condition.
The Mets issued the following statement: "A fan fell from the left-field stands and was taken to the hospital."
Gambacorta and Piacentino were among a group of MTA workers at Citi Field for a group outing.
Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. Tim Healey is an associate reporter forMLB.com. This story was not subject to the approval of Major League Baseball or its clubs.