The Spurs signed Duke to a two-way contract Thursday, Adrian Wojnarowski of ESPN reports.
Duke tallied 24 points (8-15 FG, 1-3 3Pt, 7-8 FT), eight rebounds, three assists and three steals in 24 minutes in Tuesday's Summer League game against Milwaukee.
The Nets converted Duke's two-way contract to a standard deal Friday, Brian Lewis of the New York Post reports.
Duke provided 13 points (6-11 FG, 1-2 3Pt), five rebounds, two assists and one steal in 27 minutes during Thursday's 118-113 loss to the Bucks.
Duke finished with 20 points (8-13 FG, 2-3 3Pt, 1-2 FT), five rebounds, one assist and one steal in 30 minutes Monday against the Gold.
Duke totaled 28 points (8-15 FG, 2-5 3Pt, 5-6 FT), five rebounds, four assists, one steal and one block in 35 minutes Saturday against Grand Rapids.
Duke was recalled from the G League's Long Island Nets on Wednesday, Chris Milholen of NetsDaily.com reports.
Duke recorded 25 points (10-16 FG, 3-4 3Pt, 1-3 FT), eight rebounds, four assists and one steal in 33 minutes Wednesday against Raptors 905.
Duke finished with 30 points (10-21 FG, 2-7 3Pt, 6-7 FT), six rebounds, five assists and four steals in 35 minutes Monday against Raptors 905.
Duke finished Tuesday's game against Delaware with 26 points (10-22 FG, 2-7 3Pt, 2-2 FT), six rebounds, three assists, three steals and two blocks in 39 minutes.