Experienced Starter w/First Big Contract
Dude go look at Peyton's stats the first half of that season and the second half. 10 of his 15 interceptions came in the last 8 games. After the Rams game his TD to INT ration was 10:8. His completion percentage over that stretch was 58%. 5 of his last 7 passer ratings were 85 or less. His stats pretty much got saved by the Dolphins game. He was on a record breaking pace halfway through the season. He was easily on pace to match 2013.I don't remember anyone looking at Peyton in that year and saying, "Well clearly he's going to suck next year to the tune of 9 tds and 17 ints." It's not anti-Brady to say that these things can happen suddenly. Manning went from a good quarterback to Cam Newton numbers (without the ability to run). And he was only 39. Brady is special, and I feel I have to say this again because people get riled up: I am NOT saying it is GOING to happen. Just that no season, no matter how good, is a guarantee for next year.
Then go watch the Colts playoff game. He was done. Completely done. Got worked in his own stadium. The writing was on the wall. If you think it was sudden, it wasn't. After the season he blamed it on a quad tear. So this wasn't like something that was known.
Manning being 39 is kinda immaterial too. He had a massive injury a few years before. People downplay that **** so much. There was a point where the dude could barely throw a ball and people thought his career was over. What he did was a miracle. He got himself back into game form for 2012 and slowly improved as the season went on, was raging hot all 2013, came out in the same form in 2014, then the Rams beat the hell out of him and he lost all his momentum and limped off the rest of the year and then came out next year completely done. The dude could not afford a setback like that.
Yes these can happen suddenly, but what happened to Manning didn't happen suddenly. What happened to Brees this year was a reflection of the end of last year. Brady just had his second best year for TD's, a top 5 year for yards, a top 5 completion% year (and 2 of the other top 5 are within .2 of this one so it's really more of a tie for top 3), was 1 pass attempt short of his all time passing attempts in a season, and the rest of his stats are about in line with his average. Statistically he's virtually in the same ballpark as his 2017 year (now 2017 he started out extremely hot and cooled down so it's different because for most of the year he was better than his final stats). There's really no indicators just yet.