The Swiss defender has just joined the Spanish giants from German side Bayern Munich and took Ramos’ old number after the centre back signed for Paris Saint-Germain on a free transfer.
But the 29-year-old full back insists the only reason he took Ramos’ number 4 is because nothing else was available.
He said: "We all know Ramos was here for a long time and wore this number, becoming the leader of this team.
"But the truth is that yesterday I spoke to the club and they told me that right now it's the only available squad number.
“I didn't want to start asking other players if they wanted to swap.
"I'm honoured to wear the number four, it's a source of great pride and motivation for me and I want to do it justice.
"But I'm not here to compare myself to other players or replace them, I'm here to be David Alaba."
Ramos, 35, spent 16 years in the Spanish capital, but joined the French champions last month after his contract expired. He is Spain’s most-capped player and during his hugely successful spell with Madrid, won five La Liga titles and four Champions Leagues.
Alaba, meanwhile enjoyed an even more successful stint during his spell with German champions. Having come through Bayern’s youth team he won 10 Bundesliga titles, two Champions leagues as well as six German Cups.
Speaking during his first press conference since signing for PSG, Ramos said it was “a day I will never forget”.
He said: "I am very happy to join Paris Saint-Germain.
"This is a big change in my life, a new challenge and it's a day I will never forget.
"I am very proud to be a part of this ambitious project, to be a part of this squad with so many great players.
"Paris Saint-Germain is a club that has already proven itself at the highest level.
“I want to continue to grow and improve at Paris and help the team to win as many trophies as possible."