FOXBOROUGH, Mass. -- Romeo Crennel was cautious last week when talking about the impressive potential the Houston Texans have on their defensive line with the return of a healthy J.J. Watt, Jadeveon Clowney and Whitney Mercilus.

The Texans defensive coordinator cautioned that although the team's pass-rushers are extremely talented, "you don't know how they're going to recover" from those injuries or if "they're really back."

The missed time showed early in the Texans' 27-20 season-opening loss to the New England Patriots on Sunday. The unit struggled to get to quarterback Tom Brady, especially in the first half. The Texans did not touch Brady in the first half but finished the game with two sacks (both by nose tackle D.J. Reader) and five quarterback hits.

Watt, who was playing in his first game since he broke his leg in Week 5 last season, didn't have a tackle in the first half but finished with three combined tackles and two quarterback hits. The three-time NFL Defensive Player of the Year said it took him some time to get warmed up, and he didn't feel like himself early in the game.

"I think I really started to get lathered up there by the second half, and I think that [was] just knocking some of that rust off for a full game and just getting back into a groove," Watt said. "By the second half, I definitely started to feel a little bit more and more like myself.

"Having been where I've been the last two years, I think maybe it just took a little bit of time to get back into it."

Clowney, who was the Texans' best defensive player last season but missed the spring and most of training camp while rehabbing a knee injury, said he could feel the effects of missing reps during the preseason.

"I was on the grass too much [and] a lot rustier than normal," Clowney said. "But [we've] got a lot of season left. First game. You can tell I missed a lot. But it's going to get better for me."

Watt called it a "challenge" to get to Brady because of his quick release and because the Patriots also "use Gronk [Rob Gronkowski] to chip, they use Dwayne [Allen] to chip, they use their backs to chip."

"They're going to find ways to protect, and then you've got to find ways to win," Watt said. "It's all part of the game, and they do a great job making sure that Tom [Brady]'s good back there.

"They know what they have to go up against, and they do a great job of playing against it."

The Texans have another tough test next week against the Tennessee Titans and could face mobile quarterback Marcus Mariota, who left the Titans' season opener with an elbow injury.

"I think we have a lot to improve on," Watt said. "I think there were some good things. I think there were definitely some times where we're proud of our play, and then there's some time where I wish we could have some things back."