Texans veteran running back Lamar Miller tore his anterior cruciate and medial collateral ligaments in his left knee, a magnetic resonance imaging exam confirmed Sunday, according to league sources not authorized to speak publicly.
Miller will undergo surgery to repair the damage and will be placed on injured reserve, ending his season.
The Pro Bowl alternate running back got injured Saturday night in a preseason game when he took a helmet and shoulder pad hit to the knee from Dallas Cowboys defensive tackle Maliek Collins.
The initial diagnosis for Miller was a torn ACL along with damage to the MCL, sources said Saturday night.
"It was serious," Texans coach Bill O'Brien said. "It was a tough thing to see. I think our backfield situation with depth is actually decent, but it's very difficult to lose a guy like Lamar for a lot of reasons.
"He's a great pro. He's an awesome guy in the locker room. We'll deal with it. We'll overcome it and we'll keep plugging away."
Now, the Texans will have to turn to former Cleveland Browns running back Duke Johnson as their featured back. Johnson was recently acquired via a trade in exchange for a conditional 2020 draft pick that can become a third-round draft pick if he is active for 10 games.
With the injury to Miller, the Texans will lean heavily on Johnson to fill the void.
Johnson excels as a pass-catching back, but has the capability to run the football effectively, too.
"I think it's a package deal," O'Brien said when asked how the team will handle splitting the workload after losing Miller. "It's kind of early to talk about that, to nail that down right now, but, obviously, Duke would be in there."
Signed to a four-year, $26 million contract and due a nonguaranteed $5.5 million base salary, Miller is entering the final year of his deal.
Miller had the highest average per carry of his three-year tenure with the Texans last season, averaging 4.6 yards per run and rushing for 973 yards and five touchdowns.
Miller was added to the Pro Bowl roster as an alternate following a season during which he had a 97-yard touchdown run against Tennessee, the longest rush in franchise history. Despite missing two games with rib and ankle injuries, Miller rushed for over 100 yards four times to tie a single-season career-high.
In three seasons with the Texans, Miller has 92 receptions and five touchdowns.
Miller has rushed for 5,864 yards and 32 touchdowns in seven pro seasons. He has 209 career receptions for 1,565 yards and eight touchdowns.
Miller was the best pass protector among the backs on the Texans' roster.
"It was very tough, you have a guy so special to this team," quarterback Deshaun Watson said. "He's one of the guys that bring a lot of energy and a lot of power to this team. It's tough to see him go off on the cart. Overall, just learning the offense, especially the protection side, being able to know exactly what he's seeing in the secondary, being able to have that safety decoy on play-action and things like that. He's opened up the run so much for this offense. He's a big part of what we wanted to do this season. Prayers to him."