Tashan Daniel, 20, was fatally wounded in an "unprovoked attack" on the platform at Hillingdon station on Tuesday shortly before 16:00 BST.
He had been heading to the Emirates Stadium to see the Gunners face Nottingham Forest in the third round of the Carabao Cup.
Det Ch Insp Sam Blackburn said no arrests had been made, but both suspects left the station in the direction of Auriol Drive and a knife was recovered nearby.
Thousands on the platform and at the station, cctv and yet no descriptions??!!Looks like a targeted attack despite the reports.
A West Ham fan Sami Sidhom was killed last year after a match. Noone has been charged. 'Police say Mr Sidhom was set upon by a number of attackers in the Chestnut Avenue area and stabbed multiple times.'
Meanwhile the FA and Plod concentrate on mean tweets....