NASHVILLE, Tenn. -- The best of Marcus Mariota prompts us to accelerate expectations.

And so we wonder: How can he make the judgments he did in San Diego that resulted in two killer turnovers in the midst of a game where he’s throwing three touchdown passes, topping 300 yards and running for a score?

He absolutely fumbles too much. He’s put the ball on the ground an NFL-high 17 times since he joined the Titans.

Marcus Mariota has put the ball on the ground far too often for the Titans. AP Photo/James Kenney

“He’s had several (turnovers). He’s had too many,” Tennessee Titans general manager Jon Robinson said on The Midday 180, a show I co-host. “… The coaches have done a good job of continuing to stress that. We did a lot of things this week as well, extra drills trying to hammer that home with Marcus. We want him to be able to take off and run, which he’s good at, but he’s got to protect the ball when he does so.”

With seven games left in his second season, Mariota has 18 interceptions and 17 fumbles for his career. That projects to 24 picks and 23 fumbles through his first two seasons.

That’s a lot, but let’s give it some context.

Dropping The Ball How some prominent quarterbacks fared with interceptions and fumbles in their first two seasons as starters. Quarterback INTs Fumbles Total Brett Favre 37 26 63 Peyton Manning 43 9 52 John Elway 29 20 49 Tom Brady 26 23 49 Troy Aikman 36 11 47 Marcus Mariota 24 23 47 Derek Carr 25 20 45 Cam Newton 29 15 44 Andrew Luck 27 16 43 Aaron Rodgers 20 20 40 Matt Ryan 25 11 36 Russell Wilson 19 18 37 Dan Marino 18 17 35

The chart shows turnover totals for some all-time greats and for a few prominent guys of the current era. (I look here at fumbles, not lost fumbles. What happens once the ball is on the ground is random.)

The conclusion is simple. Young quarterbacks turn the ball over more than their teams would like.

Mariota is turning it over too much, and he plays on a team that’s not equipped to make up the difference when his giveaways are especially costly. He’s got five that have turned into defensive touchdowns, the costliest brand of turnover there is.

Is their cause to believe he’ll get better? As the chart illustrates, a lot of very good quarterbacks have given the ball away frequently early in their careers and settled down as they’ve grown up in the league.

I expect Mariota will follow a similar course.