ENGLEWOOD, COLO. (AP) -- For all of the debate over Tim Tebow's development as a passer, the Denver Broncos may just need him to revert to a running quarterback come Sunday.

With top tailback Willis McGahee missing practice Wednesday following surgery to fix a broken finger, the Broncos (2-4) are down to two healthy backs, leaving Tebow as one of their leading rushing threats against the Detroit Lions (5-2).

Knowshon Moreno, who was supplanted as the starter by McGahee, and third-stringer Lance Ball took the bulk of the reps at practice. They figure to get a lot of action this weekend.

That is, when Tebow isn't making things happen with his feet instead of his arm.

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