Since the defeat in Lisbon in January, Arbeloa has made some changes, including tweaking Real's formation.

That match was the last time he played with a 4-3-3 formation, where Franco Mastantuono, Kylian Mbappe and Vinicius Jr started as the front three.

In Real's subsequent three games, Arbeloa has changed to a 4-4-2 set-up, where Mastantuono drops back into midfield to leave Gonzalo Garcia, Vinicius and Mbappe as rotating striker options.

"Defensively, it's a structure that closes down the midfield corridor, where there are more players, and allows us to be more compact," Arbeloa said.

"With the type of players we have, if we want to counter-attack, it also allows us to do so. We have a lot of room for improvement. I'm very happy because, beyond the systems, the key is effort, mentality, and teamwork, and we're achieving that."

Asked if his team is stronger with four midfielders, Arbeloa explained that "the goal is always to be solid".

"It's very difficult these days to play good football if you're not solid, compact, and don't know how to press high up the pitch," he added.

"To do all that, you need a lot of concentration, a lot of work and training. [Federico] Valverde, [Eduardo] Camavinga, [Aurelien] Tchouameni, and [Arda] Guler are doing a fantastic job [in midfield], and I don't need to tell them anything new."

Another major shift has been in squad availability. Former Liverpool right-back Trent Alexander-Arnold and Germany centre-half Antonio Rudiger have both returned after spells out with injury, strengthening Arbeloa's defensive options.

Arbeloa was particularly complimentary of Alexander-Arnold after Saturday's 4–1 victory over Real Sociedad, where the full-back provided an assist - and his coach said Real were "lucky to have" him.

"We're not going to discover anything new about Trent," Arbeloa told Real Madrid TV.

"It was a nice surprise to see how he understands the game, how he finds the spaces. Those things are very important for a coach - having players who understand what we want."

Arbeloa selected Alexander-Arnold ahead of Spain's Dani Carvajal, with both players fit again, while Valverde was restored to his preferred role in midfield.

However, Real remain without England midfielder Jude Bellingham - who is not expected back until April having injured his hamstring last month - while Brazil defender Eder Militao will not feature again this season because of a knee injury.

Raul Asencio and Rodrygo will also be absent on Tuesday through suspension.

Arbeloa acknowledged the challenge facing his side on Tuesday, pointing to the intimidating atmosphere at the Estadio Da Luz which can create relentless pressure.

"We have to give absolutely everything to win. That's always the objective," he said.

"But winning will require us to play very, very well. We must get many things right, defend well, attack well, be focused on set-pieces and play a very complete game for 90 minutes."

Arbeloa admitted Real may possess greater individual talent than their opponents, but warned leadership and belief often matter more on nights like these.

"Their spirit will be very similar to what it was three weeks ago," he said.

"They have a leader [Mourinho] who sets the course, dictating how they play and compete. From there, there are minor differences. But it will be a very competitive, tough team. And we must be prepared."

After these two teams were drawn against each other, Mourinho hailed his former club Madrid as "the king" of the Champions League.

So the challenge for Arbeloa is clear: can he ensure Real's reputation remains in tact, rather than it being stripped away in the first leg of a potentially tenure-shaping tie?