Savage was just 7-of-13 passing for 62 yards before exiting. He also lost two fumbles, including one that was returned for a touchdown. He was replaced by rookie Deshaun Watson, the Texans' first-round pick in April.
The Texans' passing game hasn't been much to write home about since Bill O'Brien took over, as the team has shuffled through a series of below-average quarterbacks. Savage, a 2014 fourth-round pick, remains one in the same. He's arguably a step up from what they had in place before, but we're not talking about a Pro Bowler here.
As such, you shouldn't downgrade the Texans' offensive weapons with Watson in the lineup. DeAndre Hopkins made things work last season; he'll be just fine with Watson under center. Don't take stock off Lamar Miller, either. He's still an RB1 in most formats.
As for Watson, there isn't much to see. You weren't using Savage, so you're not going to use his backup. He might have some value in two-quarterback leagues and dynasty formats, especially if he makes plays with his feet. But Watson didn't look great in the preseason, and O'Brien's system hasn't been conducive to much ground production in the past.
On the other hand, Watson should be an upgrade over Savage and did engineer a 14-play, 75-yard drive to start the half, ending with a touchdown pass to Hopkins. So he's worth monitoring closely but should be nothing more than a prospective buy on the waiver wire in the deepest leagues.