The superstar forward became the world's most expensive player when swapping Barca for Paris Saint-Germain in a £198m transfer after his release clause was triggered.
Barcelona chiefs were reportedly confident that Neymar would sign a new deal at the end of last season, only to be caught out when the Brazilian pushed ahead with his mammoth move.
Speaking to BBC Sport, Rakitic confessed that he is still coming to terms with his ex-teammate's decision to leave.
"For me personally, it was really hard, not only because he's one of the biggest players," he said. "But also, for me, because he's a big person. He was really important for our dressing room, and for me he's one of the best guys I know in football.
"So for me it was really a bad decision because I liked to have him in my team. We have to respect Neymar's decision to move. If a team can buy him and he decides to leave Barcelona, we have to respect it and wish him the best luck.
"Hopefully he can score a lot of goals and be happy in Paris, but we have to go on our way and be strong together without Neymar now."
Neymar has started life at the Parc des Princes in style, playing a direct part in 10 goals across his first six appearances, but he is said to have been left out of PSG's squad for this weekend's trip to Montpellier.