"He's not just another player, he's an icon," the former Bayern Munich player told reporters.
"There are players that have their own dimension and their own magnitude, like Pele, (Johan) Cruyff, (Diego) Maradona.
"Beckenbauer, he was one of those... I had the chance to meet him a few times when I was in Munich and he was very important for the club, for German football, as a player and a manager, and as a personality."
Beckenbauer died on Sunday in Salzburg, Austria, with his family announcing the news on Monday.
The Munich-born Beckenbauer won the World Cup as player and coach amid a glittering career as one of the game's finest.
He will be laid to rest on Friday at a private ceremony in Munich, while Bayern are planning a public commemoration at their Allianz Arena stadium on January 19.
"He will be remembered, he won't be forgotten because he was so big, so influential.
"It is sad but we have to be happy that we have had such big personalities in football.
"Beckenbauer is one of the chosen ones. There are not many, no more than 10, I would say."
Alonso's Bayer Leverkusen are top of the Bundesliga table, four points clear of Bayern, who have a game in hand.
