BALTIMORE -- This is what the growing pains of a rookie quarterback can look like.

Even within his strength, weaknesses are exposed as he tries to figure out how to navigate the deep waters and strong currents of the NFL.

Zach Mettenberger is an intriguing prospect in part because he's willing to stand in amid chaos and look to deliver the ball downfield. But there is a line between standing in and hanging tough and stubbornly holding on to the ball, resulting in sacks. Mettenberger crossed it a lot Sunday at M&T Bank Stadium, where the Tennessee Titans lost 21-7 to the Baltimore Ravens.

Baltimore's got a fearsome front full of threatening pass-rushers. The Ravens managed five sacks that cost the Titans 36 yards. On the majority of them, Mettenberger stuck with a play too long, unwilling or unable to settle for a checkdown or a throwaway.

"You've just got to feel pressure," he said. "When they drop out guys, you check the ball down. There is a clock in your head that's always going. And that clock goes a little faster when you've got a defensive line like they have.

"There have been a lot of immobile guys play this game and been good at it. I showed flashes today. I've just got to continue to play smart football, convert third downs, not turn the ball over."

Mettenberger was great on the team's first two drives. Tennessee moved 137 yards on 24 plays but wound up with only a 7-0 lead because the first ended when running back Shonn Greene lost a goal-line fumble.

After holding the ball for 12:50 of the first quarter, Mettenberger was 8-of-11 for 98 yards and a shovel-pass touchdown to Leon Washington, with a 130.1 passer rating. He'd hit on passes of 15, 17, 17, 15 and 17 yards. The worst third-down offense in the NFL converted four of four.

"They did a great job on the first two series," Ravens strongside linebacker Elvis Dumervil said. "We were just able to settle in."

From there, Mettenberger and the offense struggled: 8-of-16 for 81 yards and an interception, a 38.8 passer rating and five sacks. No conversions on eight third downs.

In his first start, a 30-16 home loss Oct. 26 to the Houston Texans, Mettenberger had a hard time early and was excellent late when Houston was sitting on a lead.

In many ways, this game was a reverse image.

Rookie left tackle Taylor Lewan was at fault on one of the quicker sacks. He said the line can't worry about how long the quarterback has the ball in his hand.

"It doesn't matter if he holds the ball for one second or 10 seconds," he said. "You've got to block."

The Ravens felt like a giant hit from safety Terrence Brooks on the Titans' Delanie Walker late in the first half that put the tight end out of the game with a concussion changed the tone of the game. Dumervil said it prompted Tennessee's pass catchers to change the way they ran their routes.

Titans coach Ken Whisenhunt said the softer coverage and two missed third-down passes early in the second half were the accelerants for the downfall.

On the first series of the second half, Mettenberger missed Kendall Wright short right on third-and-1. On the second, he threw behind tight end Chase Coffman over the middle.

"We missed two third-down opportunities where we had guys open in order for us to sustain drives," Whisenhunt said. "Once that happened, it put us in bad field position, which we had a really tough time overcoming.

"Had we made one of those first downs, moved the ball, whether or not we'd gotten points, it would have at least put us in position where we wouldn't have been backed up when we got the ball. That's what hurt us."

The game was already decided when the Titans took possession at their 1-yard line with 4:45 left. But Whisenhunt pointed to the play Mettenberger made there on first-and-10 as one the team will look to build on.

Mettenberger dumped the ball off to Jackie Battle on the right side and the fullback rumbled for a simple 11-yard gain.

"We've got to make sure we continue to work on that," Whisenhunt said. "Getting the ball out to the checkdowns."

Mettenberger has a big arm. He's willing to stand it against a big rush. In order for those things to matter more, the ball can't be in his hand as long and he's got to be a better dink-and-dunker.