Manning, arguably the greatest quarterback in the history of football, is not having a good season. He's 26th among qualified quarterbacks in completion percentage, 31st in yards per attempt, 21st in touchdowns, last in interceptions, second-to-last in passer rating and 24th in total QBR. His Denver offense was last in the NFL in offensive DVOA heading into Week 6 and, after a subpar performance against the lackluster Browns defense, seems likely to stay there. He's struggling. There's no way around it.
The players may not be worried, but head coach Gary Kubiak did indicate that he's going to try some things to help Manning minimize his sudden turnover issues. The story specifically mentioned not asking him to do as much on certain routes.