The midfielder struck a 63rd-minute effort for the Neroverdi but his goal ultimately proved inadequate to prevent a 5-3 home defeat at Mapei Stadium - Citta del Tricolore.
The strike has taken his season tally to four in 19 league matches involving 17 starts.
Gregoire Defrel put the visitors ahead in the 15th minute before Fabio Quagliarella doubled the lead in the 36th minute.
Ivory Coast attacker Jeremie Boga halved the deficit for Sassuolo two minutes later but Karol Linetty restored Sampdoria's two-goal cushion just a minute after the restart.
After Dennis Praet made it 4-1 for the visitors in the 46th minute, Duncan, who picked up a booking on the stroke of half-time, netted in the 63rd minute to reduce their deficit.
Manolo Gabbiadini scored again to make it 5-2 to Sassuolo before Senegal striker Khouma Babacar struck for the hosts in the second minute of injury time to leave the score at 5-3.
Sassuolo sit 12th on the league table, three places above Sampdoria.
Duncan, who has earned a Ghana recall after some time in the wilderness, will next set off for Ghana who are billed to host Kenya and Mauritania on March 23 and 26 in a 2019 Africa Cup of Nations qualifier and a friendly fixture respectively.