Four months on, the doubts appear to be justified.
The 25-year-old Cameroon international has made 11 starts for Barca in 25 La Liga, King's Cup and Champions League games and there is a niggling perception that his adaptation to the intricate one-touch style is taking longer than it should.
It may not have helped that a rash of injuries forced coach Tito Vilanova to use him as a makeshift centre back and he is competing for a starting spot with, among others, Spain international Sergio Busquets, widely regarded as one of the best defensive midfielders in the game.
In an interview with Reuters at Barca's training ground on Monday, Song appeared unperturbed by the criticism and said he and his family were enjoying life in the Catalan capital.
"I know it's not easy to start to play but I know we have a lot of games and I need just to be ready every time when the manager needs me to play and just do my job in the training," said Song, the seventh African to play for Barca.
"Sergio [Busquets] is one of the best in that position and I am very happy to train with him," he added.
"I know that when you work every single day with the top players you learn a lot and you improve yourself.
"I am happy to be here because everybody is helping me to get the most out of myself. There are not many chances to find a club like this one, with humble people who are the best in the world."
Clad in a cream-coloured v-necked sweater, jeans and white shoes with luminous green trim, Song said former Arsenal team mate Cesc Fabregas, a product of Barca's youth academy who returned to his boyhood club in 2011, had played an important role in the transfer.
Song, whose full name Alexandre Dimitri Song Billong, and his family had moved into the wealthy Barcelona neighbourhood of Pedralbes, taking the house where former France international Thierry Henry, another ex-Arsenal player who had a stint at Barca, used to live.
Song's two sons, aged four and six, have enrolled in Barca's youth academy and were learning Spanish.
"I have known him [Fabregas] for many years and he is like a brother to me, he helped and guided me," Song, who joined Arsenal as a teenager after a brief stint at French club Bastia, added.
"We grew up together, we stayed together like eight years in London. He was my captain there and he did really well."
Song still follows the Premier League and said he was sure that Arsenal manager Arsene Wenger would turn things around for the London club after a rocky start to the season.
"I think for them it's very difficult," Song said.
"But you know when you take the new players it's not easy but hopefully they will come back soon," he added.
"I think it's no problem because I know Arsene very well. He will fight to bring the club back to being successful and hopefully it will come soon because as I said it's not easy."
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