To be fair to simpleton, a lot of people buy into the myth of the cliff. However, one doesn't need to look far for proof that it doesn't really hold water. ESPN just had that "ten best since 1978" list, and we can look at that.
- Brady - TBD
- Manning - Suffered neck injury years before he retired. Signs of decline were there for years, but that decline started slowly and ramped up at the end. He still managed to win a SB in his final year. QB ratings leading up to his lost season: 121.1/104.1/101/98/95/99.9/91.9. Post-op, he had a couple of years where things went well (105.8/115.1), but the arm strength was fading. The next year (101.5) saw him losing more and more arm strength over the course of the season. His final year (67.9) saw his arm decline to the point where he was throwing balloons. Still, for as much as I love to give Manning ****, he managed some excellent play in his final years, before things finally fell apart.
- Montana - Injury after injury after injury. He went from 1985 to 1994 without playing a full 16 game season. His final 4 seasons gave him QB ratings of 89/118.4/87.4/83.6. Even after getting traded to the Chiefs, he managed to get that team to the AFCCG and then a wild card game, before sailing off to retirement.
- Elway - Elway's decline has been well documented, yet his QB rating actually went up in his later years (Thanks TD!). From 1983-1992, he only had one season with a QB rating above 80. From 1993-1998, his lowest QB ranking was 85.7. In his final season, he was able to put together a rating of 93.0, put up the 4th highest completion percentage of his career, have the 3rd best TD/INT ratio of his career, and win his second consecutive Super Bowl. Yes, his skills were eroding, but there was nothing overnight about it.
- Rodgers - TBD
- Marino - Leg injuries sapped his game and turned him into a statue, but his decline was over a 5 year period. 90.8/87.8/80.7/80.0/67.4. AYA during that time 7.2/7.3/6.6/6.1/5.2
- Brett Favre - Up and down at the end of his career QB ratings of 92.4/70.9/72.5/95.7/81/107.2/69.9. Was his last year a big drop from the year before? Damn skippy, but it was the end of a 7 year period of inconsistency and decline.
- Steve Young - retired because of concussion. In the two years before he was forced to quit, his QB ratings were 104.7 and 101.1, and he was second team All-Pro (AP) in both of those years.
- Drew Brees - TBD
- Dan Fouts - his last 5 years.... QB rating 92.5/83.4/88.1/71.4/70, TD/INT ratio 20-15/19-17/27-20/16-22/10-15, etc...
So, of the 10 QBs ESPN listed as the 10 best since 1978, only one of the seven retirees even merits an "off a cliff" argument, and that's Favre. "Off a cliff" happens, but it's nowhere near the common happening it gets made out to be, at least for the elite level QBs.