On Monday, Marrone assured Bills fans that the team's first-round draft pick is on a trajectory to succeed in Buffalo.
"I know this. I will say this. He will play to a point one day where I'm going to be able to stand here and say, 'You know what? I'm proud of him. It's awesome. He's that type of quarterback that we all want,'" Marrone said.
"He has the ability to do it, there's no doubt in my mind ... There are times when things break down and it's not necessarily his fault. Whether it be a route, a wrong route, a missed assignment up front, not winning the physical battle somewhere along the line. I think all of those things factor into play."
It hasn't been a gleaming season for rookie passers. Tampa's Mike Glennon is the surprise of the bunch, but Geno Smith of the New York Jets has been a frightful hot-and-cold act, ranking dead last among all NFL starters, per Pro Football Focus. Manuel sits just one spot above Geno, having graded negatively in every game this season save for two. Manuel's 6.3 yards per attempt rank 39th and just above the Kansas City Chiefs' Alex Smith among all qualifying passers.
In a time when quarterbacks are expected to emerge as special beings immediately, that hasn't happened in Buffalo. A full offseason will help, but the days of the project passer are over. Manuel -- like all NFL signal-callers -- faces a ticking clock to prove he's what the Bills drafted him to be.