AP photo by Mark Humphrey / Tennessee Titans quarterback Ryan Tannehill passes during practice at training camp on Aug. 28 in Nashville.

NASHVILLE — The Tennessee Titans scored lots of points and piled up lots of yards with Ryan Tannehill as their starting quarterback for just 13 games last season.

They'll soon find out how productive this offense can be with Tannehill under center from the beginning, and coach Mike Vrabel seems confident about the upside.

"I'm very happy with his grasp of what we're trying to get done," Vrabel said.

Tannehill led the NFL in passer rating last season, with the Titans' Derrick Henry leading the league in rushing. The Titans also led the NFL in red-zone efficiency — scoring touchdowns on 75.6% of trips inside an opponent's 20 — and they ranked fourth in yards per play at an average of 6.12 yards and tied for third with 54 total touchdowns.

Once Tannehill took over in mid-October in relief of former No. 2 draft pick Marcus Mariota, the Titans were even better over the final 10 games of the regular season. The Titans ranked third in both scoring (30.4 points a game) and total offense (406.2 yards per game). They led the NFL in that stretch, averaging 6.94 yards per play.

Now Tannehill has had an entire offseason and preseason to assert himself as the leader with Mariota now with the Las Vegas Raiders.

"Obviously, first year in an offense, a lot of times you're still picking it up," said Tannehill, who was traded to the Titans in March 2019 after spending the first six seasons of his NFL career as the regular starter for the Miami Dolphins. "It takes some time to get up and understand exactly the nuances of the different offenses, how you call things, how we adjust to things, how we audible things, things to look for that we can take advantage of, and so it kind of fluctuates."

This also is the second season for Arthur Smith as offensive coordinator. A year ago at this time, Smith hadn't called a play in a regular-season game. Now he has 10 offensive starters back from the group that went to the AFC championship game at Kansas City before the Titans' surprising wild-card run was ended by the Chiefs, the eventual Super Bowl champions.

"We're just continually trying to tweak what we've done," Smith said. "Is there a better way to do it? So we're constantly looking at that. You don't want to get stale, regardless of how many starters are back. But there's good familiarity of where to go, good recall on some of the stuff we've done in the past."

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AP photo by George Walker IV / Tennessee Titans running back Derrick Henry goes through a drill at training camp on Aug. 25 in Nashville.

Vrabel also sees the relationship continuing to grow between Smith and Tannehill. Teammates also are more comfortable with how Tannehill calls plays, especially when he makes changes at the line.

"We're going to continue to expand to try to give us the best chance that we can based on what looks we're getting," said Vrabel, whose team opens Sept. 14 on the road against the Denver Broncos.

There's plenty of room for improvement. Vrabel wants the offense to be more efficient on first and second downs to create more manageable yardage needs on third downs, and he also wants the Titans to commit fewer penalties before the snap.

Vrabel caught 12 touchdown passes as an NFL linebacker during his playing career, so yes Tennessee likes to use players in a variety of ways. That makes it tougher for defenses to know who will do what.

Safety Kevin Byard caught a pass last season. So did a pair of offensive linemen in Dennis Kelly and David Quessenberry — both for touchdowns. Henry threw a jump pass for a touchdown in Tennessee's playoff win against the Baltimore Ravens, with Mariota wide open to the right.

Trevor Siemian was signed by the Titans a couple of weeks ago to add depth at quarterback, and he loves everything about what the Titans do on offense, especially how the guy taking snaps is allowed to be aggressive and decisive.

"Early in my career, I was in a scheme similar for two years, and I didn't realize how good I had it playing in that scheme at the time," said Siemian, a seventh-round draft pick of the Denver Broncos in 2015. "But I've been kind peeking over the fence, so to speak, itching to kind of getting back into an offense similar to this."