So when Moon says he isn't sold on Johnny Manziel, it's commentary from a man who has been there, done that.

From left, Warren Moon, Johnny Manziel, Brett Favre (AP Photos)

Consider Moon's remarks on SiriusXM NFL Radio:

Moon, you might remember, is in the Pro Football Hall of Fame ... despite not being drafted out of college and spending six seasons in the CFL.

Here's a counterpoint: Jon Gruden says he would love to have Manziel. After comparing him to Steve Young earlier in the year, Gruden last week said he saw the flair of Brett Favre in the kid QB from Texas A&M. Gruden said, according to NFL.com:

Manziel's tryout show continues, following Saturday's workout for the Browns. He'll have more tricks up his sleeve before May 8's first-round selections.

Moon says yes, Manziel is doing all the right things to display himself to NFL teams. He knows there is competition; he knows there are teams interested, if not desperate, for quarterback help.

But …

"What makes Johnny Manziel 'Johnny' is those special, magical plays that he makes, and I just don't know if there's going to be as many of those when you're playing against the talent that he's playing against in the NFL," Moon said in the interview.

Meanwhile, Browns fans are wondering if their team is becoming overly fascinated with quarterbacks. Manziel will travel to Cleveland this week, and Georgia's Aaron Murray is due in town as well. The team also likes what it has seen from Derek Carr.

Answer: The Browns want to be ready for anything in a draft that remains a muddle.

In a mailbag for Cleveland.com, Mary Kay Cabot points out the biggest question of all: What will the Houston Texans do with the first overall pick?

The Browns likely will take a quarterback either with the fourth overall pick or at No. 26, their second pick in Round 1. Or, as Cabot notes, they could package picks and move up.

Moon's assessment, too, is correct: Manziel's game is much more suited for college than the NFL. It's probably better suited for the CFL than the NFL. And just because a guy is the flavor of the month doesn't make him a success.

Anyone remember a lefthander who was huge in college and became a pro bust? Name of Tim Tebow?

Manziel could be the second coming of Russell Wilson. Or he could be a year or two away from the end of his football career.