Nicholas Sloots, 34, was due to stand trial at Swansea Crown Court but changed his plea to guilty.
Marcus Sheppard, 37, also from Neath, died after being found seriously injured on Dalton Road, in Sandfields, Port Talbot on 27 February.
Det Ch Insp Rob Cronick said Mr Sheppard had "found himself in the wrong place at the wrong time".
He said: "The tragic death of Marcus brought shock and sadness to the community.
"We welcome today's sentencing which brings an end to the criminal investigation and I again pass on my condolences to Marcus's family who have acted with great dignity and humility throughout this horrific ordeal.
"Knife crime is unacceptable. This case shows the devastating effect the criminal use of a knife can have on an individual and their family."
A Neath man has been jailed for nine years after admitting the manslaughter of a man he attacked with a knife.