The Yellow Submarine had been frustrating the league leaders with 11 versus 11, but the match changed on the hour when Raba picked up a straight red card for a late challenge on Sergio Busquets.
Goals from Luis Suarez and Lionel Messi ultimately secured all the points for the Catalan giants, but Calleja has said that a similar challenge from a Barcelona player would have not produced the same outcome.
"Let me put it like this – if a Barcelona player had committed that foul, it would not have been a red card," Calleja told reporters.
"I have not seen replays of the incident but I got a good view of it from the dugout and it did not look like it was a red card from my viewpoint – it was part of the midfield battle. It is a shame as we were managing the game and doing well but the dismissal was the turning point in the match."