Denver Broncos coach John Fox needs heart surgery and will miss several weeks, team spokesman Patrick Smyth confirmed Saturday night.
The 58-year-old Fox will undergo aortic valve replacement surgery early this week at a hospital in Charlotte, N.C.
The Broncos did not immediately name an interim head coach. Offensive coordinator Adam Gase and defensive coordinator Jack Del Rio are expected to have added duties, sources said.
Fox had been told earlier about his heart condition and was hoping to put off the operation until after the season. As part of his trip to North Carolina over the Broncos' bye week, he met with his cardiologist and was told to seek medical attention immediately if he felt any discomfort.
On Saturday, Fox became dizzy playing golf near his offseason home in the Charlotte area and was taken to a hospital, where tests revealed he couldn't wait any longer to have the surgery.
"I sincerely appreciate all of the support from friends, Denver Broncos fans and so many around the league today," Fox said in a statement released by the team Saturday night. "Although I am disappointed I must take some time away from the team to attend to this pre-existing health condition, I understand that it's the right thing to do. I have great confidence in our coaches and players, who are fully committed to our goals.
"I look forward to returning to coaching as soon as possible."
At 7-1, the Broncos trail the Kansas City Chiefs (8-0) in their division, but they're widely considered Super Bowl favorites in the AFC.
Their next game is Nov. 10 against AFC West foe San Diego.
Sources initially told ESPN that Fox had experienced symptoms similar to a heart attack. But Smyth tweeted earlier Saturday that Fox did not suffer a heart attack.
Running back C.J. Anderson was among the players who sent their well wishes to Fox on Twitter.
Prayers go out 2 Foxy we here coach ����✊— C.J. Anderson (@CjAndersonRB9) November 2, 2013
Fox, who is in his third season with Denver, has compiled a 28-12 record with the Broncos.
Denver won the AFC West title in each of its first two seasons under Fox, who also coached the Carolina Panthers to the only Super Bowl appearance in franchise history. He's 107-88 overall, including 6-5 in the playoffs.
Information from The Associated Press was used in this report.