In an unexpected twist this season, quarterback Marcus Mariota is suddenly holding back what could—and perhaps should—be a very formidable Tennessee Titans offense.

The team made moves in the offseason to become a power offense, one that could run the ball down the throats of opposing defenses and set Mariota up for success off the back of that; however, the former Oregon Duck just hasn’t been able to do that, and in truth, the team probably hasn’t committed hard enough to that power ground game.

The Titans have run the ball an average of 30 times per game as a team. Three teams have averaged more carries per game, and none have the kind of backfield that Tennessee does (even Dallas only has one stud running back and a top offensive line, not two).

The Titans acquired DeMarco Murray in the offseason from the Eagles, who were eager to part ways with the RB, given how disastrous his first year in Philadelphia had been and the salary they were going to be paying him for that level of production. Tennessee gambled on the 2014 league rushing champion (then in Dallas), and so far this season, the gamble has paid off.

Not satisfied with that, they also drafted Alabama’s Heisman-winning running back, Derrick Henry, in the second round. Henry is 6-foot-3 and 247-pounds, providing an incredibly-bruising force to bring off the bench and hammer defenses that have worn down over the course of the game.

Those two players alone would have done a lot to lift the running game, but the Titans have suddenly happened upon the best offensive line in the game over the first six weeks of the season.

This might be the single-most unexpected performance of the season so far. Coming out of the 2015 season, the Tennessee offensive line finished 29th in PFF’s rankings. Entering the 2016 season, with the moves the Titans made to strengthen the unit over the offseason, they climbed as high as 25th, but even in the most optimistic of lights, it would have been a struggle to see this line performing as well as it has.

Taylor Lewan has gone from being a disappointing former first-round pick to the best left tackle in the game, as if a switch was simply flicked on in the offseason. Lewan owns a 92.7 overall grade, up from 83.1 a year ago, and 78.6 as a rookie. He was never as bad as many viewed him, but for him to suddenly perform like the best tackle in the NFL is a huge surprise. This season, he has yet to allow a sack or a hit on Mariota, and has surrendered a total of just five QB hurries across six weeks.

On the other side, rookie RT Jack Conklin hasn’t been much worse. He ranks sixth among NFL OTs with an 87.2 overall grade, and is the second-highest-graded right tackle—first if you discount players currently suspended for PEDs.

Conklin was a powerhouse tackle at Michigan State, but was expected to struggle in pass protection early in his NFL career. So far, that couldn’t be further from the case, as he has also not surrendered a sack or QB hit this season, and has given up just nine total pressures.

Quinton Spain, Ben Jones, and Josh Kline have all played well in stretches—and reasonably overall—to give Tennessee one of the league’s best O-lines, and a perfect platform for offensive success.

Despite all of that, Mariota's play has been dramatically worse than his rookie performance. The last two games have been better, but over the season, he has looked completely uncomfortable, unable to be particularly efficient or accurate in any area.

Even when things are set up well for Mariota, he has been making bad decisions and poor throws. Against the Browns, the Titans opened up with a read-option look, and Mariota kept the ball for a 41-yard scamper up the left sideline. The next play was 1st-and-10 from the Cleveland 34-yard line, and he almost gave it all back with an interception on a simple route combination. Waiting for his intended receiver to clear the inside route on a slant, Mariota never saw the dropping LB Joe Schobert, and threw the ball right to him.

This is a rookie mistake—only he’s making more of them as an NFL sophomore than he ever did as a rookie.

Some of his struggles are likely a result of his receiving corps, and I don’t think it’s a coincidence that his play has ticked up with the return of Kendall Wright to the lineup; however, receivers don’t explain plays like the one above.

Having a group of receivers that can't gain huge separation consistently can be an issue, requiring the QB to be smart with the football because, by definition, he is throwing the ball nearer to defenders than he would prefer; this is more than offset by having one of the league’s best ground games, though, at least on paper, and that’s before you fold in the threat of the QB on option plays. The Titans are averaging 6.0 yards per carry this season on runs that feature a read-option look, and that opening play against Cleveland shows the kind of damage it can do and the extra dimension it provides.

Right now, Mariota has one of the best situations in the league for a quarterback to be in. He can ride a powerful running game, is not under a lot of pressure (28.9 percent of dropbacks, just the 19th-highest in the league), and only needs to be a game-managing QB for this team to be successful in a weak AFC South.

If you had told the Titans before the season that the running game and offensive line would be this good at this point in the season, they would have been expecting big things from the offense overall—and from Mariota. So far, however, the QB has been the cap on the team's success, not the catalyst for even more.