Entering the day four shots behind second-round leader Brandel Chamblee, Slocum posted a bogey-free round that included six birdies and an eagle. He moved to 16-under 200 for the tournament and holds a one-shot lead over Chamblee and Andrew Magee. Miguel Angel Jimenez of Spain is two shots back.
In his second year on the PGA Tour after a successful run on the Buy.com Tour, the 28-year-old Slocum's previous best finish was when he tied for 31st at the Bob Hope Classic earlier this year. He won three tournaments on the Buy.com Tour.
With the world's top 64 players completing in the Match Play Championship, the Tucson Open has been left with a depleted field.