NASHVILLE, Tenn. -- The Tennessee Titans' secondary was like a patch of tape over a hole in the ceiling. Rain was seeping in, but it was contained. Until Houston Texans quarterback Deshaun Watson ripped the tape free and showed just how serious that problem is with a 57-14 thrashing of the Titans.

It was a record-setting day for the Texans (who scored a franchise-best 57 points) and Watson (who tied an NFL rookie quarterback record with five total touchdowns). For the Titans, it was embarrassing.

Then if things couldn't get any worse, QB Marcus Mariota left the game with a hamstring injury and didn't return. Titans head coach Mike Mularkey said he would know more Monday following an MRI. Losing Mariota for any time would be troublesome for Tennessee.

This team was built around Mariota, and Sunday was a glimpse into what the Titans would be like without him. It wasn't pretty. The loss in itself isn't cause for panic given the mediocrity of the AFC South, but what happened Sunday is very concerning.

It showed the Titans will go nowhere without Mariota, as Matt Cassel proved with a bad relief appearance in which he went 4-of-10 for 21 yards and two interceptions, including a pick-six. Cassel was a good veteran resource for Mariota, but he's not capable of running the Titans' offense and leading them to the playoffs.

Even if Mariota doesn't miss any time, the Titans need help in the defensive backfield.

Watson never looked to be in any danger, spreading out the Titans' defense and picking apart their bevy of defensive backs. The pass rush rarely got to Watson, who was sacked just once.

It was puzzling that Logan Ryan, whom the Titans signed to a three-year, $30 million contract to be their No. 1 cornerback, was covering slot receiver Bruce Ellington for many of the game's important plays while DeAndre Hopkins and Will Fuller were eating Brice McCain, LeShaun Sims and Adoree' Jackson alive.

"We did eventually. We did go that direction in the second half," Mularkey said. "I felt comfortable with what we were doing, confident in what we were doing. We've been pretty good with what we've been doing for three games. Felt like don't start moving parts if you don't have to move them. Well, we did. We moved them in the second half."

It was too late.

The Titans came into the game allowing 275 passing yards per game, 26th in NFL. It was actually worse than their pass defense in 2016, when they gave up 269 yards per game.

Hopkins abused McCain on slant routes. Fuller's speed left Jackson committing a costly pass interference penalty and Sims getting left behind.

Titans defensive coordinator Dick LeBeau shifted to rushing just three defenders in the second half in hopes of helping plug leaks in the secondary, but it only got worse.

With a win, the Titans would have been in position to separate from the AFC South pack. Instead, they have just as many if not more questions than the rest of the division.