Officers were called to Salford Royal Hospital at about 23:45 GMT on Friday by staff who reported a 28-year-old had been admitted with stab wounds to his neck, shoulder and chest.
He had been helped to the hospital by friends after being attacked on Edward Street.
Det Sgt Julie Connor said it was a "brutal attack" with an unknown motive.
"What we do know from the doctors is that the victim is lucky to by alive and if his friends had not intervened, he would probably have died from blood loss," she said.
The man's attacker was described as being white, in his early 20s, and of average height and slim build, with brown hair cut in a 1960s style and a scruffy beard or moustache.
He was said to be wearing a blue top with a circle emblem on the front and blue jeans, and was carrying a large carving knife.
Det Sgt Connor said anyone with information about the attack should contact police.

Two other former executives, as well as the camera firm itself, filed a guilty plea in Tokyo District Court.
They face up to 10 years in prison.
The three admitted to hiding losses dating back to the 1990s, which were brought to light by a former chief executive, Michael Woodford.
'Entire responsibility'
Mr Kikukawa said he regretted not revealing the accounting irregularities earlier.
"There is no mistake. The entire responsibility lies with me," Mr Kikukawa said in court on Tuesday.
He also apologised for the trouble caused to investors, customers, employees and the general public.
The scandal was revealed when Mr Woodford, the British chief executive, was dismissed from his post after he challenged Mr Kikukawa and the board over suspiciously large payments related to acquisitions.
An investigation was launched that revealed a cover-up of losses.
Mr Kikukawa, former executive vice-president Hisashi Mori and former auditing officer Hideo Yamada were arrested in February and later indicted on suspected violation of the Financial Instruments and Exchange Act.
A man who suffered "numerous stab wounds" in an attack in Salford is "lucky to be alive", police have said.
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Former Olympus chairman Tsuyoshi Kikukawa has pleaded guilty to charges of falsifying accounts, covering up losses of $1.7bn (Â£1.1bn), at the opening of his trial.