Steadily, but quickly, Vance Joseph is filling out the offensive side of his coaching staff.

The Denver Broncos have reached agreements with Mike Sullivan to be their new quarterbacks coach and Curtis Modkins as their new running backs coach, sources told 9NEWS.

Sullivan was the New York Giants' offensive coordinator the previous two seasons. He had worked previously with Broncos' offensive coordinator Bill Musgrave in Jacksonville during the 2003 season.

In this handout image provided by the NFL, Mike Sullivan of the New York Giants poses for his 2010 NFL headshot circa 2010 in East Rutherford, New Jersey.

The Broncos also considered Ben McAdoo and Ken Zampese for the position, but both were holding out for offensive coordinator positions.

Klint Kubiak, who had served as the Broncos' interim quarterbacks coach, is expected to remain on the team's staff in another capacity.

The Broncos have another Mike Sullivan. He is in charge of overseeing the Broncos' salary cap and contracts.

In this handout image provided by the NFL, Curtis Modkins of the Buffalo Bills poses for his NFL headshot circa 2011 in Rochester, New York

Modkins has been an NFL running backs for 10 years. He most recently served on John Fox's staff with the Chicago Bears, where Jordan Howard rushed for 1,122 yards and Tarik Cohen was one of the NFL's most exciting rookies.

The Broncos had already hired former UTEP head coach Sean Kugler to coach their offensive line. Joseph, the Broncos' second-year head coach, has four other assistant coaching positions to fill: Receivers, outside linebacker, special teams coordinator and assistant defensive backs.