West Ham fans travelling to Greece this week will be wrapped in a protective police cocoon after Olympiacos' most recent match was abandoned amid a vitriolic atmosphere at the Karaiskakis Stadium.
Olympiacos warmed up for West Ham by hosting Panathinaikos – a game otherwise known as the 'Derby of the Eternal Enemies'.
That Sunday showdown in the Athenian port of Piraeus was halted at 1-1 after a visiting player was reportedly hospitalised when struck by a firecracker.
In what could be problematic, UEFA have allowed Olympiacos and Panathinaikos to play on the same day on Thursday, facing West Ham and Rennes respectively in the Europa League. It means fans of four different football teams will descend on Athens this week.
West Ham supporters are being warned that they can only get to Olympiacos' Karaiskakis Stadium via a compulsory coach convoy – complete with a police escort – meeting at the Panathenaic Stadium more than three hours before kick-off.
Police in Athens say these protocols are in place for their own safety and that anyone who does not use the coaches will risk being turned away from the arena.
Supporters are also set to be subjected to rigorous body searches and locked inside the away end for 30 minutes after the final whistle before being returned to the Panathenaic Stadium via their appointed transport.
Meanwhile, West Ham are also aware of the possibility of laser pointers being pointed at their players.
Greek supporters were accused of shining lights at opponents during their recent 1-0 loss to the Netherlands at the OPAP Arena in Athens, with Virgil van Dijk among those targeted.
As part of their standard dialogue with local authorities, the Premier League club are learning the latest on security protocols for their staff and supporters ahead of travelling.
The Karaiskakis Stadium can be one of Europe's most challenging grounds to visit, and Panathinaikos say their abandoned game against Olympiacos will be 'decided in the courts'.
Their player, Juankar, the 33-year-old Spaniard, was warming up down the touchline before being taken away on a stretcher midway through the second half.