The Catalan skipper, who recently agreed a "lifetime" contract with the four-time European champions, is concerned that Coutinho's arrival could see him spiral down the pecking order at the Nou Camp.
According to Diario Gol, Iniesta has told members of the Barcelona hierarchy that Coutinho is not needed, despite the club having seemingly made a breakthrough in attempts to bring the Brazil international to Spain.
Mundo Deportivo understand that Liverpool are willing to allow Coutinho to leave for a fee approaching €150m [£134m] and that a deal could be completed in the January transfer window.
Agent Kia Joorabchian reportedly informed club officials - in London for The Best Fifa Awards - of Liverpool's demands during a meeting this week.
But Barcelona's overtures are threatening to upset their skipper, who is perturbed by the prospect of Coutinho's arrival. Such a deal would eclipse the €147m the club have agreed to pay for Ousmane Dembele.
Croatia international Ivan Rakitic is also concerned by Coutinho joining the current La Liga leaders and fears his place in the team could be put under severe pressure should the move be completed.
Both Iniesta, 33, and Rakitic 29, are already conscious of the impressive start made by summer signing Paulinho since his move from Guangzhou Evergrande and the progress made by Sergi Roberto and youngsters Denis Suárez and André Gomes, all of whom featured in the 3-0 Copa del Rey win over Real Murcia on Tuesday [24 October].
If Barcelona do pursue a move for Coutinho in spite of these protestations they could choose to deploy him on the left side of the attack, where he currently plays for Liverpool; a position in which the club have few options.
Dembele is expected back in the new year after surgery on a torn tendon in his hamstring but the onus on maintaining Barcelona's fine start to the season will continue to rest on the shoulders of Lionel Messi and Luis Suarez, who have netted 18 goals between them this term.