No one has questioned Zach Mettenberger's arm strength or his NFL potential.

He was widely considered one of the most talented quarterbacks in the draft, someone who played well for most of his three seasons at LSU.

A guy like that shouldn't be around in the sixth round, but he was, and the Titans snatched him up Saturday.

In time, Mettenberger could turn out to be a home run. Yet it's also fair to forecast failure for the second Titans pick of this draft carrying some red flags.

"The jury is still out on me, and I am going to do everything I can to prove everyone wrong, that I am a great player and I am a great person," Mettenberger said on a conference call. "… I took a long hard road to get to where I am, and now I am an NFL player. I'm ecstatic for the opportunity."

It's easy to understand why Mettenberger is getting a chance.

The 6-foot-5, 224-pounder has a cannon for an arm, can make all the throws and has the gunslinger mentality that often causes NFL scouts to drool. He passed for 3,082 yards and 22 touchdowns in 2013.

"They say a quarterback's talent is in his arm, and that is the case for him," Titans general manager Ruston Webster said. "He throws the ball really well."

So what's the knock? The list includes an injury, an arrest and a failed drug test. It clearly scared teams and resulted in Mettenberger being the 10th of 14 quarterbacks drafted.

The Titans traded their sixth- and seventh-round picks to the Redskins to move up and select him.

"We'd heard that there were other teams that were trying to move up to get him," coach Ken Whisenhunt said. "At that point, we felt like it was a low-risk-high-reward type of situation."

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Mettenberger tore an anterior cruciate ligament in November and didn't take part in drills at the NFL Combine in February. He said he's healthy now.

He produced a diluted urine sample at the Combine, but his trainer said it was the result of over-hydration. Mettenberger declined to answer questions about it on Saturday. Whisenhunt also declined to discuss it, citing NFL rules.