7:40 AM PT -- Turns out the mystery man is Eli Bronfman -- the super wealthy grandson of late billionaire Edgar Bronfman Sr. -- who was the chairman of Seagram.
Emily and an apparent new date were chatting it up courtside Wednesday night as the Knicks defeated the rival Pacers, 119-113.
The duo was definitely giving first-date vibes, but seemed to have some chemistry ... and even arrived together outside the Garden.
Once they were inside, the soap-esque plot twist became apparent ... as Eric was also enjoying the game.
The comedian didn't publicly make any contact with Emily -- with whom he recently went on a date -- but did do some celeb hype for the cameras and other Knicks fans.
It looks like he might've gotten the better seats than ER this time around, because he showed off his perfect view.
As we reported, Emily and Eric enjoyed a romantic evening together in NYC over the weekend, going out for food, drinks ... and presumably lots of laughs.
Emily's been super active on the dating scene since she filed for divorce from estranged husband Sebastian Bear-McClard in September ... the 31-year-old model's been linked to DJ Orazio Rispo, artist Jack Greer and, of course, Pete Davidson.
FYI -- Emily and Pete also hit up MSG in November, sitting courtside together after trying to maintain a low profile for a while.