Commonwealth Games gold medallist Jamie Arthur fell to his second successive defeat in Edinburgh on Saturday.
Coventry-based South African Harry Ramakgoadi put Arthur on the floor in the first and the Newbridge man, 25, never fully recovered his senses.
He was dropped twice more in the fifth before the referee stopped the bout.
Wales' Taz Jones also suffered his second defeat, a points loss to Colin McNeil of Scotland in a fight for the vacant Celtic light middleweight belt.
It is difficult to see the direction Arthur's career will take now, though.
His previous defeat, against Haider Ali in January, was caused when a clash of heads opened a bad gash.
But the Welshman believed he had overcome his problems with cuts and was confident under the direction of new trainer Enzo Calzaghe.
Ramakgoadi, 29, takes his record to 15-5-2 (2 KOs).