The sports broadcaster said Karl told the team he will undergo an intense, six-week chemotherapy treatment regimen but indicated it was a "very treatable and curable" form of throat cancer.
Karl was quoted as telling Nuggets players he discovered a lump on his neck six weeks ago, and after a biopsy, it was determined he was again facing cancer. The Denver coach has been cancer-free since prostate surgery in July 2005, ESPN said.
"I don't know that I've come to terms with this yet," he said. "I have friends and family praying for me and the whole spiritual aspect is keeping me strong. But I'm not Superman."
ESPN said Karl indicated he would undergo 35 cancer treatments during six weeks and had determined to keep his condition private until after he had finished coaching the Western Conference All-Star team Sunday.