Peter King, citing a 49ers source, says unrealistic expectations in San Francisco might have been a turn-off.
"SB-or-bust feel would have bugged PM," King tweeted.
There's no sense in criticizing Manning for what a 49ers source perceived the quarterback's motivations to be. We cannot say for certain whether Manning feels that way. Surely there were multiple reasons for his decision, some of which might never become known.
The reality, however, is that anything short of a Super Bowl appearance with Manning indeed would have qualified as a disappointment for the 49ers. And there were no guarantees the 49ers were going to advance that far, even with Manning.
Much was made of Manning's potential aversion to facing his brother, Eli, in the NFC playoffs. Aaron Rodgers, Drew Brees, Matt Ryan and Matthew Stafford also carried deterrent factors relative to most of their AFC counterparts.
If the 49ers offered the best team situation for Manning, the Broncos or any AFC contender offered a clearer path to the Super Bowl.
New England, Baltimore, Houston, Denver, Pittsburgh and Cincinnati were the top six teams in the AFC last season. The NFC was much stronger with Green Bay, New Orleans, the Giants, Atlanta and Detroit standing in the 49ers' way.
Very good teams with very good quarterbacks fall short every year -- especially when faced with stiff competition within their conference.
Last season, Green Bay went from the cusp of 16-0 to one-and-done in the playoffs, losing at home to the Giants. The 49ers barely outlasted New Orleans in the divisional round with Alex Smith making plays even Manning could not duplicate, notably a signature 28-yard touchdown run deep in the fourth quarter.
San Francisco went 13-3 last season. Manning beat that record only twice during his 13 seasons as the Indianapolis Colts' starting quarterback.
The 49ers, 6-2 on the road last season, travel to face the Packers, Saints and Patriots outside the NFC West in 2012. They could have finished 12-4 with Manning and regressed. The Broncos can go 11-5 with him and point to a three-game improvement in the standings.
The blowout defeat Denver suffered to New England in the divisional round suggested the Broncos were championship pretenders.
From Manning's perspective, however, he's joining a team that won a playoff game without a consistent passing threat and in a conference without as many contending teams. If the job comes with lower expectations at the outset, all the better.