This is awful, as anybody who knows Jim Johnson can tell you. Even if you only know of him, the news of his leave of absence to resume chemotherapy treatments just grabs the air out of your chest. This is a good man, and a tough man, and the idea that he is involved in this kind of a struggle is disheartening. If prayers and good wishes and hopeful thoughts matter, Johnson will get through this -- because his friends and admirers in a tough business are legion.
In the meantime, Sean McDermott runs the Eagles' defense. He is young, only just 35, but he has been in the building for 11 years now. He actually pre-dates Andy Reid, arriving as an assistant in the scouting department in 1998. When Reid got here, McDermott became assistant to the head coach. Those are great stepping-stone jobs in the NFL -- you see everything and learn everything and work your ass off, and then you work your way up from there. This is what McDermott has done, from quality-control coach (another work-your-ass-off/learn-the-business job), to coaching both the secondary and the linebackers with the Eagles.
Is McDermott ready? You never know until you know, obviously, but it is hard to believe somebody could be better prepared to run this system. And if track record matters, people named Leslie Frazier, Ron Rivera, Steve Spagnuolo and John Harbaugh (for a season) have all worked under Jim Johnson and all gone on to success in other places. We all have talked and written in the past about the connection Johnson has had with his players, but there is a clear connection with his coaches, too.
Again: you never know until you know. But as we wait and hope for Johnson's return, there is every reason to believe that Jim has taken care of the interim as he now takes care of himself.