Since he took over as the Denver Broncos starter in 2011, Willis McGahee has been one of the most consistent running backs in the NFL. This year, he’s been the top running back for the second-highest scoring offense in football.

Now, Peyton Manning will have to hand the ball off to someone else for, perhaps, the rest of the season. McGahee will miss six to eight weeks with a torn ligament in his right knee.

The injury comes at a time when the Broncos are playing as well as any team in the league. Denver has won five straight, and leads the San Diego Chargers by three games in the AFC West.

With the easiest part of their schedule coming to an end, the Broncos will need a running back to step up and come close to replacing McGahee’s production. Entering Week 12, the trade deadline is long over, and Denver’s best chance is for someone already on their roster to catch fire.

Knowshon Moreno may have the best chance of matching McGahee’s level of play. He’s a former first-round draft pick, and has shown flashes in the past of having the talent to play at an elite level.

In 10 games, McGahee averages 73.1 yards per game, good for 12th in the NFL. Moreno has been inactive for the last eight games, recovering from a torn ACL that he suffered last November.

Even before his injury, Moreno was already on his way to being labeled a “bust.” He got just 37 carries in seven games last season, and was replaced by a running back that hadn’t rushed for 1,000 yards in four years. His best year came as a rookie, when he ran for 947 yards in 2009.

The Broncos hope that Moreno’s time on the inactive list will benefit him. For most of the season, he’s had time to recover from his injury. Because he hasn’t been playing every week, he should be less banged up than almost any active rusher. Manning is the best Broncos quarterback since Moreno was drafted, and perhaps his play will improve from having a future Hall of Famer under center.

If Moreno can’t get the job done, Denver has a few unproven options.

Ronnie Hillman and Lance Ball have both seen more time than Moreno this season, with Hillman getting 49 carries, good for second on the team. In his rookie year, Hillman is averaging 3.8 yards per carry, but hasn’t shown many signs that he can be a No.1 back. Since entering the league in 2008, Ball has never run the ball more than 96 times in a single season.

Head coach John Fox will likely go with some kind of combination of the three to start. The back that performs the best could take over the top spot in McGahee’s absence.

McGahee might be out for the remainder of the regular season, but he hasn’t been placed on injured reserve. The Broncos first game without him is on Sunday against the Kansas City Chiefs. Kansas City has one of the worst rush defenses in the league.