Sofyen Belamouadden, from Acton, west London, suffered multiple stab wounds during a fracas at Victoria Underground station, in central London.
His family spoke of their anguish and branded the teenager's attackers "cowards with no respect for life or the people they leave behind".
His uncle said that the teenager played football for Acton Garden Village Youth Sunday League team in West London and for Chelsea Kicks, a scheme run by the Premier League club for young people in deprived areas.
A spokesman for the club described Sofyen as a "talented footballer" and a "valued participant" on the scheme.
The detective leading the murder investigation said he believes Sofyen may have died during a pre-arranged fight.
Det Ch Insp John McFarlane, from the Metropolitan Police, said: "A number of individuals travelled by various bus routes to Victoria carrying weapons."
Detectives were holding 19 boys aged between 15 and 17 who are mainly from South London. At least two knives were recovered from the scene of the attack.
A man in his 30s who was also arrested was later released with no further action to be taken.
Witnesses said a gang of attackers wearing school uniform chased the victim from the busy station concourse into an Underground ticket hall.
More than 2,600 people joined a Facebook group called RIP Sofyen.