Matheus Franca's last-minute goal for Crystal Palace foiled Southampton's hopes of securing only their third victory in the Premier League this season and brought them dangerously close to an unwelcome record.
Franca, who came on as a substitute, scored a late header to salvage a 1-1 draw for the Eagles, putting Southampton at risk of relegation if they lose to Tottenham and Wolves defeat Ipswich over the weekend.
If Southampton's relegation is confirmed on Sunday, they will become the first team to be relegated with seven matches remaining in the season.
Despite reaching double digits in points for the season, Southampton still remain one point away from matching Derby's record low points tally of 11.
Crystal Palace came into the game at St Mary's on the back of a five-game winning streak and a morale boost from reaching the FA Cup semi-finals, with manager Oliver Glasner even being linked to Bundesliga side RB Leipzig.
Palace, aiming for a seventh consecutive away victory, almost opened the scoring in the opening minutes when Jean-Philippe Mateta struck the crossbar with a powerful shot from long range.
Saints took a surprise lead in the 20th minute when Mateus Fernandes provided a cross for the towering Onuachu to nod home, breaking Palace's run of clean sheets away from home since Christmas.
Despite chances at both ends, it was Franca's late goal that ultimately leveled the score, leaving Southampton in a precarious position near the bottom of the table.
The match ended in a 1-1 draw, with Palace coming close to snatching a win in the dying moments, but Nketiah's effort flew narrowly over the bar.