Let's break this down a little...
Here is the exact quote as being reported by ESPN:
One source who spoke with Manning prior to his visit with the Cardinals said "his gut is that Manning is leaning toward Denver."
Considering that Manning is traveling alone, the only sources that could have "spoke with Manning" would be those affiliated with the Broncos in Denver, since he departed that city on a Cardinals jet. It seems a given that anyone in Denver associated with the Broncos would relay optimism or a positive "gut feeling" to the media. What else are they going to say "No, we don't feel good about our chances"? Even if the visit to Denver went horribly wrong, they aren't going to admit that to anyone, especially the press, until long after Peyton makes his decision.
Nothing to worry about here, IMO.