A 26-year-old Chilean man has been missing since New Year's Day.
He is described as a tanned man, with short dark-brown hair and is around 5ft 5ins tall.
He was last seen wearing a yellow Arsenal away shirt with number 17 on the back, navy blue shorts with socks to match and white Nike football boots (with orange ticks).
Police are concerned for Alexis' welfare and want to hear from anyone who may have seen him or who has information on his whereabouts.
It has been claimed they were searching the Southampton players' pockets soon after their 2-0 win over the Gunners but their hunt has been to no avail.
He is known to frequent North London and surrounding areas, as well as partaking in journeys to Premier League grounds across the country every other week.