The pair both opted to leave Bayern Munich, with Alaba making a free transfer to Los Blancos in 2021, and Lewandowski completing a controversial switch to Catalonia this summer.
As teammates in Bavaria, the duo won seven Bundesliga titles, and a 2020 Champions League, but the prospect of a new challenge in Spain swayed them.
“I am not surprised with Lewy. I know him very well from my time in Munich”, he said.
“What he’s doing in Spain, I experienced first hand for years in Munich.
“He’s one of the best strikers in the world. He has shown it time and time again and he is showing it this season.”
Despite his positivity over Lewandowski, Alaba stuck to his Real Madrid connections in terms of the 2022 Ballon d’Or race, with the Austrian tipping Karim Benzema to win it.
Alaba and Lewandowski are set for their first meeting in Spanish football next weekend, as Barcelona head to the Spanish capital on October 16.