South Shields saw their five-game winning streak end at the hands of Curzon Ashton in the Vanarama National League North.
Issac Sinclair's brace gave player-manager Craig Mahon's side all three points at the Tameside Stadium.
Josh Ollerenshaw in the Nash goal gave a Man-of-the-Match performance, keeping a clean sheet and making some vital saves for the hosts.
Shields were without top scorer Paul Blackett after picking up a wrist injury during Good Friday's derby clash with Spennymoor Town.
Curzon made three changes to the side who beat Banbury 4-1, as Alex Kenyon, Hayden Campbell and George Waring made way for Marcus Poscha, Stefan Mols and Luke Griffiths.
The Nash took the lead three minutes into the game through Isaac Sinclair who was gifted the ball after Mahon's deflected cross landed to the midfielder who wrong-footed Myles Boney in the Shields goal and saw his effort slot in the bottom left corner.
Josh Ollerenshaw would prove to be the thorn in Shields' side throughout the game as he kept out Aaron Martin and Dylan Stephenson's chances in both halves.
Ollerenshaw managed to tip Martin Smith's long-range effort onto the crossbar in the 13th minute.
Despite the Nash shot-stopper conceding a lot of corners, he and his defence managed to clear the ball almost every time.
Shields would come closest in the 23rd minute when Ollerenshaw would have to be at full stretch for two chances that looked like certain goals only four yards out but Curzon's goalkeeper managed to clear the danger.
It would be the same story for Elliott Dickman's side in the second half as the chances kept coming, but Ollerenshaw would be the only thing standing in their way.
Sinclair got his second of the game in the 59th minute as his shot beat Boney and the ball headed towards the bottom corner to extend Curzon's lead.
Shields would continue to pile on the pressure to the hosts but the defending and goalkeeping of Ollerenshaw proved to be too much for the Mariners.
The result sees the teams swap places in the table, as Curzon climb to sixth and Shields drop to eighth, outside the play-offs on goal difference.
The Mariners host already-relegated Bishop's Stortford on Saturday 6th April.
South Shields: Boney, Hunter, Briggs, Broadbent, Adams (C), Smith, Jenkins, Heaney (Woods 61), Clarke (Savage 61), Stephenson (Gomes 80), Martin
Unused subs: Abbey, Sloan