"With a new No. 23 jersey on his back and a football grasped tightly in his right palm, Willis McGahee shadowed running backs coach Eric Studesville at Broncos training camp Sunday afternoon.

During the 2 1/2-hour practice, McGahee never strayed far from the running backs. And each time starter Knowshon Moreno finished a play, McGahee gave him a high-five or a slap on the shoulder.

Denver, meet your new running back tandem.

"There's no more one-back systems here in the NFL," McGahee said, joking that he and Moreno could be nicknamed "Stallions and Horses."

"I'm just going to come in and do the best I can," said McGahee, 29. "I'm going to help him out, and whatever plays I can make, I'm going to make."

The Broncos signed McGahee, a former first-round draft pick from the University of Miami who played the first eight years of his NFL career with Buffalo and Baltimore, to a four-year contract Sunday morning after he passed his physical. He isn't allowed to practice until Thursday.

"This is a new beginning, a new start," McGahee said. "It's wide open right now."

Broncos head coach John Fox was adamant throughout the offseason that he wanted to add a running back in free agency to strengthen the team's running game. The Broncos hope to have a run-based offense this season, a switch from the pass-happy offense of the past few seasons directed by previous head coaches Josh McDaniels and Mike Shanahan.

At 235 pounds, McGahee has the potential to complement the newly slim Moreno, who arrived at Dove Valley weighing about 200 pounds. Moreno expects to remain the starter, but McGahee is considered a better runner between the tackles and in short-yardage situations, a serious weakness for the Broncos in recent seasons. Last year with Baltimore, as Ray Rice's backup, McGahee had only 100 carries. But he scored five touchdowns.

One of those touchdowns - a 30-yarder - came against the Broncos."