The South Africa-born forward had already been ruled out of the Six Nations, which begins on Saturday, but now faces a period of rehabilitation, with no indication as yet when he might be fit to return.
Before suffering neck injury problems this season, the 30-year-old had been tipped as a potential Lions Test starter but that hope now appears over.
Nel’s club, Edinburgh, explained in a statement yesterday: “Willem Nel has undergone surgery on a neck injury sustained in his side’s win over Harlequins at Twickenham Stoop on Saturday 14 January.
“A MRI scan on Wednesday 18 January at Spire Murrayfield Hospital revealed that Nel damaged an intervertebral disc in his neck during a significant collision during the game. Following further assessment, surgery was deemed as an appropriate course of action.”
Nel first hurt his neck in the home game against Harlequins last October. He was told to rest for four weeks but that stretched to two months before his comeback in the return European Challenge Cup with the London side lasted just 25 minutes.
Scotland coach Vern Cotter named Nel in his Six Nations squad but it was soon confirmed that he could play no part in the tournament.
“I will wait until we have professional advice on it,” Cotter said two weeks ago. “Of course there are concerns. I would like to know more, but there are concerns.”