Diallo came to the United States in 2007 to play for Rochester Raging Rhinos in the USL First Division. During the 2007 season with Rochester, Diallo was a regular starter up front along with English-born strikerMatthew Delicate; however, during 2008 Diallo gradually became a less frequent member of new coach Darren Tilley's squad, and had only eventually logged 474 minutes of playing time in 13 USL matches during the 2008 season.[3]
On July 9, 2008, Diallo was transferred to Carolina RailHawks in return for Jamil Walker. Diallo produced a top-notch season with RailHawks in his debut season, where he recorded a hat-trick against the Seattle Sounders despite losing the match on a score of 4–3. He finished off the season by scoring seven goals and registering three assists in 16 games to finish with a team-leading 17 points. Despite a promising debut season, Diallo unfortunately failed to regain his previous form that dominated the 2008 season; which led to limited playing time during the 2009 season. On March 8, 2010, the Real Maryland Monarchs announced the signing of Diallo to a contract for the 2010 season.[4]