Halton McCollin died three days after he was shot
Police are offering a £20,000 reward in the hunt for the killers of a 20-year-old man they believe was the victim of mistaken identity.
Halton McCollin, 20, was shot in the head in the China Garden in Stretford in January and died three days later.
Greater Manchester Police say they can protect witnesses who come forward with information on the murder.
They also want to hear from someone who rang officers with information on the night of Mr McCollin's shooting.
An incident three days earlier when shots were fired at two young people on Talbot Road in Stretford may be linked to the killing.
Police believe the gunman may be among those who killed Mr McCollin, perhaps mistaking him for their intended target.
Det Supt Sam Haworth, of Greater Manchester Police, said: "There are definitely people who do know who killed Halton.
"If you are one of these people, I urge you to ask yourself again whether the people you are protecting are worth it.
"Halton's family are constantly waiting to hear that his murderers have been caught.
"You might not believe us when we say we can protect your identity completely, but it has been proven in court.
"We do not underestimate the bravery it takes to come forward, and we do not seek to pretend it makes for an easy life.
"This is partly the reason we have secured this money, as a financial reward for taking this step."
Three men are believed to be involved in the shooting of Mr McCollin, who played semi-professionally for Flixton Football Club.
Two masked men were seen running towards the takeaway from a nearby alley just before the shooting, while a third walked up the road past the Gorse Hill pub.
Two of the masked men then ran into the China Garden and fired three shots, one of which hit Mr McCollin.