The subpoena is related to the investigation into Aaron Hernandez, the former Patriots tight end who was college teammates with Pouncey at the University of Florida, according to SI.com's Pete Thamel and Greg Bedard.
Authorities are reportedly focusing on Hernandez's potential involvement in interstate gun trafficking in at least three states: Massachusetts, New York and Florida.
The extent of Pouncey's involvement is unknown but SI.com reports that "police are focusing on multiple transactions that involve him and Hernandez."
Dolphins spokesman Harvey Green said "Organizationally, we do not have a comment," adding: "And Mike Pouncey does not have a comment."
More details via SI.com:
A grand jury subpoena does not mean Pouncey, 24, has been or will be charged with a crime. Rather, law enforcement officials regard him as a material witness who could advance their case against Hernandez. Dolphins officials indicated Pouncey would be traveling back home with the team Sunday night.
After the game, two members of the Massachusetts State Police in dark suits approached Pouncey in the hallway between the Dolphins locker room and the team bus and handed him a piece of white paper. "It's about a grand jury investigation," one official could be heard telling Pouncey. The same police official later said, "Make sure you arrive."
Pouncey appeared confused when handed the paperwork by police and said, "What's this about?" Soon Dolphins officials were scrambling around the concourse looking for answers.
Dolphins director of security Stu Weinstein told SI.com "You need to talk to [general manager] Jeff Ireland or [coach] Joe Philbin," and a uniformed Massachusetts State Policeman declined comment altogether. A Patriots official said team owner Robert Kraft was not made aware of that Pouncey would be served with a subpoena.
Pouncey and his twin brother Maurkice, a center with the Steelers, were close to Hernandez and all three lived together at times during college. The Pounceys were photographed over the summer wearing "Free Hernandez" hats. And though Maurkice later apologized, Mike never did.
The Steelers declined comment to SI.com, including whether Maurkice Pouncey had been served.