Philadelphia Eagles defensive coordinator Jim Johnson is taking a leave of absence.
Johnson is beginning a second round of chemotherapy to deal with cancer, which has him confined to a wheelchair.
Johnson won't coach at the upcoming OTAs -- organized team activities -- a three-day rookie camp beginning Wednesday.
"I told him to take care of himself first, and when he's ready to come back, come back," Eagles coach Andy Reid said Monday.
"I'd like to tell you he's great, but he's not. He's struggling right now," said Reid, who said he talks to Johnson every day by phone. "I told him, when you feel like it, come back."
Secondary coach Sean McDermott will coach the Eagles defense in the interim.
Johnson, 67, complained of back pain in early January. He coached from the press box in a playoff win over the New York Giants and in the Eagles' loss to the Arizona Cardinals in the NFC championship. An MRI after the playoff win against the Giants on Jan. 11 alerted doctors that something might be wrong.
Johnson was treated for melanoma in 2001. Following the Arizona loss, the team announced the cancer had returned.
"He's struggling," Reid said Monday. "But he's a tough guy and a true battler."
Johnson had recovered sufficiently to coach during the team's first post-draft minicamp earlier this month.
But he coached from a motorized scooter during practices and said wasn't sure if he could return to the field for the upcoming season.
"It's too early to tell," Johnson said May 2. "I'm taking this one day at a time or one camp at a time. I'll just keep working at it, and as long as I can hold my work schedule I'll feel fine, and we'll just see how it goes."
Reid said he hopes Johnson, who has spent the last 10 years as the Eagles' defensive coordinator, is able to return to the team soon.
"I hope everyone will keep him in their thoughts and prayers during this period of time," Reid said.
Johnson is known for his aggressive, attacking style and has played a significant role in the team's success over the last decade. Last season, Philadelphia finished third in total defense and fourth in points allowed as the Eagles advanced to the NFC title game for the fifth time in the last 10 seasons.
Information from ESPN's Sal Paolantonio and The Associated Press was used in this report.