Buffalo Bills general manager Brandon Beane said the franchise was caught off guard by running back James Cook sitting out practice due to his desire for a contract extension.

"It's not something we were fully aware of until shortly before practice," Beane said Monday on WGR550, according to The Buffalo News' Katherine Fitzgerald. "So, I get it, I understand it; it's the world we're in, I guess, of how players want to respond and things like that."

Beane added: "At the end of the day, I wish we weren't here. This is my ninth season here, we've never had a player miss due to a contract or anything like that, so that's disappointing for me."

Cook isn't practicing again Monday after missing his first session of training camp Sunday, according to The Athletic's Joe Buscaglia. The rusher cited "business" as the reason he's abruptly chosen to sit out of Buffalo's on-field activities.

The 25-year-old is entering the final year of his deal, which has a $5.27-million base salary for the 2025 campaign. He signed a four-year rookie contract in 2022 after the Bills selected him in the second round of the draft.

Beane said the two sides haven't stopped negotiating on a potential extension throughout the offseason.

"Without getting into things, there's been constant communication with his agent, either with myself or Kevin Meganck (vice president of football administration)," Beane said.

"Unfortunately, it takes two. And both sides have to agree on what that number is. And obviously that hasn't gotten there."

Cook has been Buffalo's top running back over the last two campaigns and led the NFL in rushing touchdowns (16) in 2024. The Georgia product has 3,521 total yards and 27 scores in 49 career contests.