The LaLiga leaders claimed a point in Turin on Tuesday that guarantees they progress to the next phase as winners of Group D, despite having started the match with Lionel Messi surprisingly on the bench.
Chances were few and far between at the Allianz Stadium but Ter Stegen made two decisive stops, denying Douglas Costa in the opening two minutes before producing an excellent reaction save to prevent Paulo Dybala scoring a winner in second-half stoppage time.
Remarkably, Ter Stegen has saved 23 of the last 24 shots on target he has faced in all competitions for the Catalans, and Iniesta believes the German has become a key component of the team.
96% - Marc-Andre ter Stegen has saved 23 of the last 24 shots on target he has faced for Barcelona in all competitions. Show. pic.twitter.com/S7wzudpXrs— OptaJose (@OptaJose) November 22, 2017
"We know Ter Stegen's quality and he still has room to improve," Iniesta told beIN SPORTS. "He makes the difference and the Barcelona goalkeeper, against the few things that come his way, has to be successful. In that sense, he's splendid."
He continued: "We achieved our objective of finishing first after a great effort. It will all help us to continue improving.
"We did a great job to be top of the group, which is the goal we've had since the opening day."
Iniesta was given a standing ovation by some of the home fans after an impressive midfield display, and he was thankful for the recognition.
"I'm grateful for the support the fans always show me," he said.