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."

Baggs, 27, who ran a communications firm on the Isle of Man, was found dead at a his home in the island's capital Douglas at about 09:00 BST on Thursday.
In a Facebook tribute, his sister Charlotte Baggs described him as "the biggest character".
Police are investigating his "sudden and unexpected" death.
A spokeswoman said there was nothing "to indicate that his death is criminally suspicious".
She added: "Police again confirm that at this time there is nothing obvious to indicate the cause of his untimely death and inquiries will continue. The police request that consideration is given to the privacy of the family and friends at this difficult time."
When he appeared on the BBC One show in 2010 aged 21, Plymouth-born Baggs was its youngest contestant.
The series was won by Stella English, but he became a cult favourite with his steady stream of catchphrases and his description of himself as "Baggs the brand".
In her Facebook post, his sister Charlotte wrote: "Today my dearest brother Stuart Baggs gained his wings. To say we are all shocked and devastated is an understatement.
"Love him or hate him, he touched many people's lives from his TV antics to his amazing work with Bluewave Communications."
She added: "He was the biggest character and will leave the biggest hole behind. Not knowing what or why makes it all the harder.
"Can't explain how proud I am of him. He was the king of following his dreams and making them happen."
Past and present stars of the show show took to social media to express their shock at the entrepreneur's death.
The Apprentice boss Lord Sugar said: "Terrible news Stuart Baggs has died. My sincere condolences to his family and friends RIP one of the stand out characters of the apprentice."
Countdown host Nick Hewer, who left his role as Lord Sugar's adviser this year after a decade on the show, tweeted: "So sad to hear of Stuart Baggs' death. Condolences to his family. He will be remembered with affection by all who knew him on Apprentice 6."
Dara O Briain, former presenter of spin-off programme The Apprentice: You're Fired! wrote: "Sad news about the death of Stuart Baggs. Interviewed him on You're Fired and he was funny and self-effacing. Condolences to his family."
Dr Lear Totton, a cosmetic doctor and winner of the show in 2013, tweeted: "Just heard the sad news that Stuart Baggs has died. His 'I'm a whole field of ponies' line was one of my favourite ever from The Apprentice. RIP x"
Former contestant Luisa Zissman tweeted: "RIP one of my favourite ever Apprentice contestants Stuart Baggs "The Brand" he has joined the 27 club. What a tragedy".
Baggs, who launched his company Bluewave Communications in 2007, gave an interview to the Isle of Man Examiner last week about his latest scheme to bring 4G broadband to the island.
Talking about his career, he said: "I work, as my hair will tell you, at least 18 hours a day. I sleep for four hours religiously, I would not have it any other way, like Margaret Thatcher."
He said that work gave him "a buzz", adding: "As to the future we are already working on that."
A Neath man has been jailed for nine years after admitting the manslaughter of a man he attacked with a knife.
[NEXT_CONCEPT]
The sister of former Apprentice contestant Stuart Baggs has said the family's world has been "shattered" by his sudden death.