Semi Ajayi made his maiden appearance for West Bromwich Albion in their 1-1 draw against Rotherham United in a pre-season friendly game on Tuesday.
On Saturday, the 25-year-old midfielder completed his move to the Hawthorns, signing a four-year contract with the side.
The Nigeria international was handed a starting role against his former club but endured a difficult debut appearance on his return to the New York Stadium.
Ajayi’s late challenge on Freddie Ladapo led to a penalty and the Anglo-Nigerian calmly slotted home his effort to give Paul Warne’s men the lead.