Houston Texans coach Gary Kubiak is optimistic Arian Foster will be ready for the regular-season opener after the star running back re-aggravated a hamstring injury in Saturday’s preseason game in San Francisco.

Foster, the NFL’s leading rusher in 2010, left the field in the first quarter of Houston’s 30-7 victory, favoring the left hamstring that he strained early in training camp.

Foster sat out Houston’s preseason opener, then rushed five times for 47 yards and two touchdowns in the Texans’ 27-14 win over New Orleans on Aug. 20. He was hurt on his eighth carry against the 49ers.

“Looks like we’re dealing with the same thing we were dealing with at the start of camp,” Kubiak said Sunday. “Hopefully, we can get him back on the rehab train, and get him ready for opening day. He’ll be day-to-day.”

Kubiak said head athletic trainer Geoff Kaplan offered a “very positive” outlook for Foster’s recovery, though Kubiak stopped short of saying Foster would definitely be healed in time for the Sept. 11 opener against Indianapolis.

“Until he hops back out there, there’s a concern,” Kubiak said. “But it sounds like we’re heading in the right direction.”