That or he's got some real rotten luck.
To me it's more a matter of having inferior teams and having a few close, tough losses strung into something, over years, to give the wrong impression.
One of the things Peyton haters love to chant is one and dones. But look at those.
2003: 0-41 loss to the Jets. Horrible loss. Everyone should be ashamed of how they did in that one. Peyton was awful. 0 tds, 2 int and all of 137 yds. That's a guy playing a very bad game and a team doing likewise.
2006: a 21-18 loss that wasn't embarrassing for anyone. That Steeler team beat Denver next, in Denver, 34-17 in route to winning the Super Bowl 21-10 over Seattle. So the best contest they had in that playoff run was against Indy.
2008: a 28-24 loss to a very good and very balanced San Diego team that would do it to them again a year later. Peyton threw for over four hundred yards, 3 tds and 2 picks. Rivers threw 3 tds against 1 pick. The Chargers put up about a hundred yards. The unbalanced Colts couldn't make fifty, which meant they could tee off against Peyton and smother the passing game...well, as much as you can without getting in the back field with him.
2009: 17-23 loss to those same Chargers. Peyton threw for 310, 1 td and 0 picks. The Colts managed 64 yds rushing. The Chargers? Rivers turn to have a bad day, with no tds and one pick, but the Chargers ran for 167 yds and that was the clock controlling difference.
2011: 15-17 loss to the Jets. A defensive battle with one of the best defensive minds doing what he also did to New England, keep it low and tight and hope for something. Peyton? Over a hundred qbr but neither team could move the ball consistently. The Jets offense stunk but their defense was magnificent. It's a two point game.
2013: 38-35 over time loss to the Ravens. Tough loss to the eventual SB champion that never should have reached over time.
The last debacle I've discussed. He shouldn't have been in the game with torn quads and no ability to really plant, which showed in the last few games and after a couple of hits he was done.
So that's one Peyton not getting it done and one injury game out of those seven. With the right team he could have as easily been the winner of five of them. So the one and done losses really reduce to a guy who was good enough to pilot teams to seven opportunities, not a guy who choked and lost them.