HOUSTON (AP) — Deshaun Watson looked rusty in Houston's season-opening loss to New England, committing two turnovers and failing to move the offense consistently in his return from knee surgery.

Now the second-year quarterback must find a way to improve before Houston begins AFC South play on Sunday at Tennessee where the Texans will be without right tackle Seantrel Henderson.

Coach Bill O'Brien said Monday that Henderson is out for the season with an ankle injury. O'Brien added that Henderson, who was brought in this offseason to improve Houston's line, will have surgery on Tuesday.

O'Brien said that for Watson to play better this week the rest of the offense has to pitch in to help him.

But he did admit that Watson was a little rusty and that he has "to make better reads, better decisions" for the Texans to be successful. O'Brien was also quick to point out that Watson is still a young player so growing pains are to be expected.

"It's only I think his seventh game as a starter in this league," O'Brien said. "He hasn't played football in ... a regular-season game, in a while ... there's a little bit of rust involved in all of those things and I know that he will improve. He'll work very hard to improve, but there's a lot of work to do."

After Henderson was injured late in the first quarter on Sunday the Texans looked to rookie third-round pick Martinas Rankin to fill in. O'Brien thought he did a nice job and could look for him to do more with Henderson out for the season.

Rankin said it was a bit daunting to be thrown into action unexpectedly, but that having a positive attitude helped him succeed.

"Just telling myself: 'No fear. I belong here. They brought me here for a reason and I'm going to represent this organization the best I can,'" he said.

When asked about regaining the tempo the offense had in the six games Watson started last season, O'Brien lamented the fact that they started things off on a bad note when Watson fumbled a handoff on the team's first offensive play.

"That's just horrendous," O'Brien said. "To give the ball on the 15-yard line or whatever it was, 20-yard line, going in first play of the game, that's no way to start a game. So, it starts there."

The good news for the Texans is that Watson improved as the game went on, leading the team to two touchdown drives late after settling for field goals early in the game. He should get a boost this week with the return of receiver Will Fuller, who missed the opener with a hamstring injury.

The speedy Fuller has shown promise as a deep-play threat in his career, but Sunday was the 11th game he's missed because of injury in his three-year career.

While Watson didn't have a great game against the Patriots, the Texans did get a solid performance from their running game.

Lamar Miller led the way, rushing for 98 yards after not running for more than 75 yards in 16 games last season. Houston also got a nice game from backup Alfred Blue, who added 36 yards rushing and a touchdown.

"The line blocked well. I thought when we got into a rhythm in the running game, it was good," O'Brien said. "We rushed for almost 170 yards, which was obviously one of the highlights for us on offense. I thought that Lamar ran hard. Lamar's a good pro, he does a good job of reading the runs and getting us good yards."

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