Greater Manchester police (GMP) said the victim "ran across the road" after the stabbing and collapsed inside a restaurant.
He has been taken to Manchester Royal Infirmary and his injuries "are thought to be serious".
Police said they were pursuing two men in connection with the attack. The pair, both described as black men of medium build in their late 20s to early 30s, walked away from the scene before getting into a silver A3 Audi TDI.
One was wearing a grey t-shirt with black writing on it while the other wore a black hat and a thick black coat. Police have appealed for witnesses.
This afternoon's incident follows a shooting incident last night in the city's Moss Side area. A 16-year-old boy was shot at outside his home, apparently by one of three unidentified men.
He was with four contemporaries, none of whom were believed to be over 16 years old. The boy discovered afterwards that he had a scratch and burn mark by his left ear, caused by a bullet whistling past his head.
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