Frank Reich has a history with Philip Rivers as he spent several years as an assistant coach with the Los Angeles Chargers.
Now the pair have reunited with the Indianapolis Colts.
"Obviously, when it came out that Philip was going to be available, it was an easy discussion to see that it was a fit with us," Reich said.
"Does he still have it all left in the tank at 38? What does he have left in the tank at 38? Just having been there on the inside for the three years I was and knowing the quarterback position like I do, I was so confident that physically he was the right player and that he had not lost anything. All of the throws I saw on film and as I go back and studied him compared to previous throws, I really didn't notice any physical gifts diminishing at all. I really didn't."