It's the same prognosis for right guard Brian Winters, who re-dislocated a shoulder and may require surgery -- which clouds his future with the team.
The Jets (2-7) are getting pounded by injuries on both sides of the ball. They already have 11 players on injured reserve, including wide receiver Quincy Enunwa, linebacker Avery Williamson and cornerback Trumaine Johnson.
Winters and Herndon figure to be the 12th and 13th.
This has been a nightmarish season for Herndon, a key component in the passing game. He was suspended four game for violating the league's substance-abuse policy, then missed another four due to a pulled hamstring.
He played only 16 offensive snaps in Sunday's 34-27 win over the New York Giants, catching one pass for seven yards. He received an X-ray after the game, with a CT scan Monday confirming the fracture.
Herndon will be sidelined "an extended period of time," coach Adam Gase said, adding the fracture is located in a place "where if something happened, it could really hurt him worse."
Quarterback Sam Darnold said recently the offense would be "unstoppable" once Herndon returned. The offense, which has produced only 11 touchdowns in nine games, has fallen well short of expectations.
"I feel bad for Chris because he was excited to get back out there," Gase said. "For whatever reason, he couldn't catch a break this year."
The Jets will continue with Ryan Griffin, tied for the team lead with three touchdowns, as their lead tight end.
Speaking of Winters, Gase said "it will be hard to get him back this season." Winters, 28, the second-longest tenured player on the roster, has battled injuries throughout his career. This will mark the fourth time in the past six years that he ends the season with an injury.
His cap charge in 2020 is $7.5 million, the final year of his contract, and there's a chance he could become a casualty of the anticipated offensive line overhaul.
Winters was replaced in the third quarter by Tom Compton, who likely will remain the starter. The Jets will have their sixth different offensive line combination Sunday when they face the Washington Redskins.
"He's a really good player, a really smart player," Darnold said of Winters, who had played every offensive snap until Sunday. "To lose a guy like that, a player like that, it's a bummer for this team, this offense and really for the whole organization."
Winters will become the seventh offensive starter to miss multiple games.