Ed Zurga, Associated Press
Denver Broncos running back Willis McGahee (23) is helped from the field during the first half of an NFL football game against the Kansas City Chiefs at Arrowhead Stadium in Kansas City, Mo., Sunday, Nov. 13, 2011.

KANSAS CITY, Mo. — The Denver Broncos lost running backs Willis McGahee and Knowshon Moreno to injuries in the first quarter Sunday and still managed to beat the Kansas City Chiefs.

John Fox isn't sure when either will be available given Denver's short week.

McGahee hurt his hamstring near the end of the Broncos' opening drive, and although Fox said he was available in an emergency, their leading rusher never returned. Moreno went down later in the first quarter with a sprained knee.

The Broncos held on for a 17-10 victory Sunday, but they'll have a quick turnaround with a game against the New York Jets scheduled for Thursday night.

"We'll find out, maybe not until Tuesday. That's when we form up for practice," Fox said, when asked if either running back will be ready for the Jets.

McGahee had surgery a couple weeks ago to repair a broken right hand, but he came back last week to run for 163 yards and two touchdowns in a 38-24 win over Oakland. He picked up where he left off against Kansas City, carrying four times on the opening possession.

Moreno was even more effective, breaking loose for a 24-yard run during which he hurdle Chiefs cornerback Brandon Flowers, and a 22-yard run later in the quarter. It was at the end of that carry, near the Denver sideline, that Moreno came up hurt.

"That didn't help our cause, that's for sure," Fox said. "We've overcome that before. We had a Cincinnati game where we got low on receivers and guys stepped up."

The Broncos, who have implemented a run-heavy scheme behind option-style quarterback Tim Tebow, were left to use wide receiver Eddie Royal out of the backfield a few times along with third-string running back Lance Ball and fullback Spencer Larsen.

Ball carried 30 times for 96 yards, and the Broncos still ground out 244 yards on the ground.

"It felt good," Ball said. "It didn't even feel like 30 carries. I just kept on plugging, trusted my guys, trusted my O-line and we popped a couple when we need it. That felt great."

The Broncos only threw eight times, and Tebow completed just two of them, though one was a 56-yard touchdown pass to Eric Decker in the fourth quarter that helped seal the win.

"We had some good things going on with the running game, and back and forth with different backs," Tebow said. "It was unfortunate that two of them go down, but Lance really stepped up and Spencer stepped up and played well for us."