Walker is finally back from suspension, having served a three-match European ban in the aftermath of his red card against RB Leipzig in the group stage that left manager Pep Guardiola furious.
Defensive colleague Dias, meanwhile, has been out injured for six weeks and while Guardiola confirmed the Portuguese would not start at the Wanda Metropolitano this evening, he did confirm that he has at least travelled with his team-mates.
“He did one training session after six weeks off,” Guardiola said at his pre-match press conference on Tuesday. “It is premature, but the fact he is back with the schedule we have is good. Everyone will be important and Ruben is.”
Kevin De Bruyne scored the winner at the Etihad Stadium to give the visitors a 1-0 aggregate lead in Madrid, before the Premier League leaders secured a 2-2 draw in the meeting with Liverpool on Sunday.
Guardiola has plenty of options on his bench to freshen up his line-up amid a busy run of fixtures with Ilkay Gundogan, Riyad Mahrez, Jack Grealish and Fernandinho his options to come into the XI.
City face Liverpool again in the FA Cup semi-finals at Wembley on Saturday.
Predicted Man City XI: Ederson; Walker, Stones, Laporte, Cancelo; Gundogan, Rodri, De Bruyne; Mahrez, Jesus, Sterling.