NASHVILLE, Tenn. -- Tennessee Titans quarterback Marcus Mariota didn’t shine on deep balls as a rookie.

I watched him throw throughout training camp practices and never felt like his arm was insufficient for such throws. He had bad receivers and little time thanks to poor protection, which factored in.

The early evidence in games is he’s not going to be a huge deep-ball thrower.

But I was struck by context offered by this tweet from Mike Renner of Pro Football Focus.

15+ yard outs, hitches, & comebacks accounted for 2.8% of all attempts in NFL last year. We can stop glorifying their importance any day now — Mike Renner (@PFF_Mike) April 11, 2016

Now that doesn’t factor in other deep stuff -- posts, corner routes, go routes, etc. But it’s still a very interesting nugget.

It makes me wonder about cause and effect.

Do those routes account for so little because play-constructors and playcallers don’t like them, don’t think they will work or simply prefer other stuff?

Or are those routes “unimportant” because coaches know their players can’t make them work, starting with quarterbacks who can’t find the time or make the throws?

Either way, Mariota’s deep numbers, including those throws but not limited to them, were poor.

Per ESPN Stats and Info, he was 23rd in the NFL on throws that traveled at least 15 yards in the air, completing 39.5 percent of his passes. He threw 7.1 of them a game, 16th in the league.

Passes of 20 yards or over were really nonthreatening: He was 35th, dead last among qualifying quarterbacks, with a 16.7 percent completion percentage.

He completed just seven such passes, fewer than Johnny Manziel, who dropped back 198 fewer times.