The venue's famously hostile atmosphere has never been kind to Madrid, who have failed to win in four previous visits, drawing three and losing one.

Alonso arrives in Piraeus amid a mini-crisis, with his side winless in their last three matches across all competitions.

A 0-1 defeat to Liverpool was followed by goalless frustration against Rayo and a 2-2 draw with Elche, leaving the manager seeking a strong reaction in what is shaping into his first major test since taking charge.

Madrid sit seventh in the League Phase on nine points, and a victory would bolster their top-eight ambitions, while another setback risks pulling them into the playoff scramble.

Complicating matters is a deepening injury crisis. Thibaut Courtois has been ruled out with gastroenteritis, handing Andriy Lunin another start.

In defence, Eder Militao, David Alaba and Dani Carvajal are all unavailable, with Antonio Rudiger doubtful due to a hamstring issue.

Raul Asencio is the only fully fit senior centre-back, though Aurelien Tchouameni is expected to return and partner him. Olympiacos, 31st with just two points, desperately need a result to keep their hopes alive.

"We need a good performance and, after these last few matches, to get back to winning ways," said Alonso.

"To do that, we have to play well, stay focused and realise that this is an important match for our position in the table.

"Despite having nine points, we want to add more. After the Liverpool match and the next two league matches, we want to get another result tomorrow.

"I follow Olympiacos not only because we knew we'd be playing them in the Champions League, but also because I have a lot of personal appreciation for Mendilibar and Darko Kovacevic.

"I know what they achieved in the Conference League and what they achieved last year. Mendilibar is a top-class manager and someone who promotes very intense football.

"He has achieved that at Olympiacos and is receiving the recognition he also had at Eibar and other clubs. I'm really happy that he's getting it here."

Ansu Fati's Barcelona future in doubt amid limited opportunities