Miller exited Saturday's game in the first quarter after taking a hit to his left knee.
Texans running back Lamar Miller tore his ACL in Saturday's preseason game against the Cowboys, according to NFL Network's Ian Rapoport.
Miller was carted off the field with an apparent left knee injury during the game. He exited early in the first quarter after Cowboys defensive tackle Maliek Collins' helmet hit him in the knee. The running back landed awkwardly, and medical personnel quickly asked for the cart to be brought to the field. Taiwan Jones came in to replace Miller.
According to Rapoport, an MRI confirmed the ACL tear on Sunday.
The 28-year-old Miller, who made his preseason debut on Saturday, is Houston's best pass protector and runner. He tallied 973 rushing yards with five touchdowns in 14 games last season. Duke Johnson Jr., who the Texans recently acquired in a trade with the Browns, is listed behind him on Houston's depth chart.