Speaking ahead of his pre-match press conference for the Champions League tie, Demichelis recalled reaching out after Argentina's World Cup semi-final win over England.
Reflecting on their close bond and his former captain's leadership, Demichelis said: "At the time I was a very close team-mate of his in the national team group. When Leo got married, I was one of the guests. I never liked bothering Leo through messages, because I imagine he must have millions every day.
"After the semi-final I wrote to him because I felt a need to congratulate him after the match against England, where once again he showed, in a very special way, how to bring out that gut feeling as a team and as captain.
"That conviction of his, his gaze, his desire and above all his age... Wow! I felt the need to congratulate him, to ask him, for one last time, to enjoy it, regardless of what came afterwards."