Marcus Mariota worse this season under center, vs. blitz, with midrange throws

NASHVILLE, Tenn. -- His calm and poise translated to the NFL right from the start.

In Tampa Bay on Sept. 13, 2015, Marcus Mariota led the Tennessee Titans to a 42-14 win, completing 13 of 15 passes for 209 yards and four touchdowns.

The rest of Mariota's rookie season had its ups and downs for sure, but even after missing four games with two knee injuries he finished the year having established that Tennessee had found its long-term answer at quarterback.

Four games into his second season, his passer rating is down 17.6 points, from 91.5 to 73.9. He looks uncertain. He's off target. He's throwing more interceptions than touchdowns. And he's created a slew of questions.

So what's changed? What's wrong? Let's run through a bunch of answers.

Scheme: Ken Whisenhunt was hell-bent on getting all five eligible players out on routes, which often meant insufficient protection help for a struggling line. Head coach Mike Mularkey and offensive coordinator Terry Robiskie are more willing to keep tight ends or backs in as needed, and that's contributed to the better protection for sure. But what exactly is the Titans' exotic smash mouth? The Titans have hardly forced the issue running the ball. Their 107 attempts are tied for ninth-most in the league. Some of the exotic stuff has looked far too cute and failed. Robiskie said last week: "Our goal is to be the best running team in ball, the best executing team in ball and one of the most physical teams in ball." When a team has a talented young quarterback and he's not mentioned when the offensive coordinator lays out the team's primary goal, it's puzzling.

Pass protection: It's way better. Left tackle Taylor Lewan has hurt the team with penalties, but he's playing well. Jack Conklin and Ben Jones have been what they had hoped. Josh Klein may be better at left guard than was Chance Warmack, the injured player he replaced. Mariota was sacked on 10.3 percent of his attempts last year, and that number is 5.1 this season. Logic says Mariota would be better with better protection, but he has not been.

Targets: Out went athletic but raw and unreliable receivers Justin Hunter and Dorial Green-Beckham. In came more technical, precise route runners Tajae Sharpe, Rishard Matthews and Andre Johnson. But the precise bunch is being imprecise, according to Mularkey, which strikes me as more frustrating than raw guys failing in that department. And the Titans sacrificed speed in the transition. No one is scared of this offense throwing deep.

Motion: The Titans motion and shift constantly, to a degree that seems like it could tire them out -- physically, if not mentally. Mularkey said it's all done with a specific purpose. And clearly it helps slow down how a defense spaces out and times up blitzes. But it's far more extensive than it was in Mariota's rookie season.

Position coach: John McNulty is coaching tight ends in San Diego. Mularkey wanted continuity for Mariota, so when he put together his staff, he moved Whisenhunt's offensive coordinator, Jason Michael, to quarterbacks coach and let McNulty go. I thought McNulty did good work with Mariota, and keeping him would have meant continuity in the position that deals most closely and most regularly with the quarterback. Did the Titans keep the right coach?

Running: Mariota appears reluctant to run. He's taken off just 13 times for 72 yards with Mularkey talking about how he thinks a quarterback is actually subject to fewer dangerous hits outside the pocket. By design or as he improvises, the Titans are not getting enough from a dynamic that makes defenses nervous. Last year, Mariota ran on 5.9 percent of his snaps. This year: 5.2 percent. He's lost two fumbles this season to go with six in 12 games a year ago. Ball security was one of his big focuses in the offseason. Does he trust himself to hold onto the ball, or is that part of what he's not taking off?

Run game: The run game is significantly better, with DeMarco Murray the NFL's fourth-leading rusher. That was supposed to set up play-action which would make things easier for Mariota. But in 2015 he had a 96.5 passer rating on play-action plays. This year that's plummeted to 76.5. And they are not running much more play-action as was the plan. It's 7.5 snaps a game right now vs. 8.25 plays a game in Mariota's 12 starts in 2015.

Under center: Another side-effect of the run game, where Murray excels with the quarterback under center, is that the Titans intended to run less shotgun, in which Mariota has more experience. Last year he was 11.3 points better in passer rating when under center as opposed to in shotgun. This year he's 32.1 points worse. Ponder that. As for the idea he'd be under center more: This year's ratio -- 56.1 percent shotgun, 43.9 percent under center -- is almost exactly the same as last season's.

Against the blitz: This is drastically different. As a rookie, he completed 64 percent of his passes when teams came after him and posted a 104.0 passer rating. This year it's 45.9 percent and 50.1. Something big has changed with his ability to recognize what is coming at him and to handle it.

Throws between 10 and 20 yards: Passes between 10 and 20 yards in the air ought to be bread-and-butter range for Mariota. They were last season, when he had a 109.7 passer rating and threw five touchdown passes and two picks. This season he's awful in this range -- with a 39.3 rating, no touchdowns and three picks. He missed 26 such throws -- an average of 6.5 a game. That's a lot. That's too much.