The Catalan giants waved goodbye to the legendary playmaker last month in an emotional sendoff following 22 years of service.
Iniesta, who won 32 trophies across 16 seasons in Barca's senior ranks, is due to start a new chapter in the Far East following Spain's World Cup campaign.
Philippe Coutinho was brought in during the January transfer window and others have also been linked, but Abidal admits that the hole left behind by the 34-year-old will never be truly filled.
"We will make the decisions according to the needs of the team," he told reporters. "But we cannot replace Iniesta with a player of the same quality, that's impossible."