HOUSTON -- The good news for the Carolina Panthers on Thursday night was they improved to 3-0, but the concern is whether they can sustain their success after losing two of their biggest stars in running back Christian McCaffrey and cornerback Jaycee Horn.

Or is it?

“We’re a football team," left tackle Cameron Erving said after the 24-9 victory over Houston. “We’re not the Carolina Christian McCaffreys."

McCaffrey suffered a hamstring injury with 12:13 left in the second quarter and did not return. Horn, who was the No. 8 pick overall in this year's draft, went down with what coach Matt Rhule called multiple breaks in his right foot in the third quarter and was carted off.

There was no immediate timetable for when either will return.

Quarterback Sam Darnold and the league’s top-ranked defense were enough to hold off the Texans, but they might not be enough when the competition picks up in Week 4 with Dallas on Oct. 3.

McCaffrey entered Thursday’s game as the NFL leader in yards from scrimmage. Not only is his productivity as a runner and receiver valuable, but his blocking is also important.

“Losing Christian is tough, but I thought we did a good job of bouncing back," Darnold said. “For us, it’s just executing the plays called. It’s as simple as that for us. Just because Christian is out doesn’t mean I’m not going to go to the running back."

Darnold wasn’t sacked prior to McCaffrey's going down without contact on a run to his left. Darnold was sacked three times the remainder of the second quarter after McCaffrey was replaced by rookie Chuba Hubbard.

Darnold took the blame for that, saying he held on to the ball too long trying to force the play downfield.

Asked what the Panthers learned about Darnold in the second half when the former Jets quarterback completed 14 of 16 pass attempts for 146 yards, Erving said, “We’ve got a good one."

Darnold also rushed for two touchdowns, something he’d never done in a game since arriving in the NFL in 2018.

As for Horn, his ability to man-up on the opponent’s top receiver allowed defensive coordinator Phil Snow to attack with more blitzes. That helped Carolina to a league-best 10 sacks the first two games. Whether that will continue against more experienced quarterbacks remains to be seen. The Panthers had four sacks Thursday.

Houston (1-2) was the second of Carolina’s three opponents to start a rookie quarterback.

Horn was replaced by veteran Rashaan Melvin, who was signed to the practice squad on Sept. 14 after being released after training camp.

Rise of TE Tommy Tremble: The rookie out of Notre Dame did little in the first two games but emerged as a weapon in the second half of this one with a rushing touchdown on an end around and a 30-yard catch. He might be evolving into offensive coordinator Joe Brady’s scheme.

Quarterback breakdown: Darnold struggled some immediately after McCaffrey left, in large part because his protection broke down. But he took his game to another level in the second half in a way he hadn’t the first two games. He beat the Texans with his arm and legs, almost willing Carolina to victory -- finishing 24 of 34 passing for 304 yards.

Silver lining: After next week’s game against Dallas, the Panthers get the Philadelphia Eagles, Minnesota Vikings, New York Giants and Atlanta Falcons.