The Senegal international headed home from Cuco Martina’s cross after earlier assisting Gylfi Sigurðsson for the opener in his 17th appearance this season to help Sam Allardyce’s men secure their ninth top-flight win.
And Pickford is not surprised by the display of the former Lokomotiv Moscow player after showing similar performance in training.
"I did not know what he [Niasse] would be like aerially [when he first signed],” Pickford told club website.
"But I was kicking the ball up and he was winning his share of battles.
"The lads were putting balls in the box and he got on the end of a few of them with headers as well. That is promising.”