Patriots center David Andrews' "season is in jeopardy" because of blood clots on his lungs, ESPN.com reported, citing unidentified league sources.
Andrews, who was undergoing tests to pinpoint the cause of the clots, reportedly was released from the hospital Monday night.
The Athletic, which cited unidentified league sources, initially reported that the longtime starter and captain since 2017 was expected to miss "significant time" because of the condition.
Andrews played 28 snaps in the Patriots' preseason win over the Panthers last Thursday but wasn't at practice Sunday or Monday.
His absence could deal a major blow to the defending NFL champions' offense in terms of leadership, in-game communication and his strong rapport with quarterback Tom Brady.
Although Andrews, 27, went undrafted out of Georgia in 2015, he became a starter for New England in 2016. He has played in 60 NFL regular-season games, starting 57. By comparison, Andrews' backups, Ted Karras and James Ferentz, are entering their fourth season but have combined to start only five games in their NFL careers.
The Patriots have been to three consecutive Super Bowls since he earned the starting spot and won in two of those appearances.