The Gladbach goalkeeper will move to Camp Nou in the summer to replace Victor Valdes but must step up to be good enough for the Blaugrana first team.
On Friday, Goal confirmed that Barca had reached an agreement with Borussia Monchengladbach to sign the goalkeeper this summer for a fee in the region of 9-12 million euros.
Since breaking into the Gladbach first team three years ago, Ter Stegen's stock has continued to rise and rise. He was first thrust into the first starting XI in the place of Logan Bailly as a teenager and helped Lucien Favre's side survive relegation against the odds. He was the star of the show, along with Marco Reus.
The following season saw Gladbach produce more brilliance. Stunningly consistent, the club pipped Bayer Leverkusen to fourth place in the 2011-12 Bundesliga. Ter Stegen was again one of the key players - only Bayern Munich had a better defensive record in the division - and was duly rewarded with an international call-up shortly after his 20th birthday.
The following term was far more of a disappointment for the Foals, who dropped to eighth place in the table and conceded twice the number of goals they had the previous season, while failing to make it into the Champions League proper after slipping to a disheartening defeat to Dynamo Kiev in qualifying.
So, the question remains: is a 21-year-old of such little top-level experience ready to play for one of the biggest clubs in the world and, beyond that, fill the void of a club hero like Valdes, who is arguably enjoying his finest season with the Blaugrana?
Ter Stegen has never featured in the Champions League proper and was hardly a bastion of stability against the Ukrainian outfit in qualifying, conceding a slack goal at his near post.
Beyond that, Germany has lost in each of his three appearances for the national team. The first was a goal fest, a 5-3 loss to Switzerland, with the young keeper culpable for one of the strikes.
Three months later, he was thrust into action against Argentina after Ron-Robert Zieler was dismissed and his first action was to save a Lionel Messi penalty. Things went downhill from there, though, as Germany slipped to a 3-1 loss.
The nadir was in the post-season tour of the USA. When given a chance to impress against the home side, Ter Stegen failed miserably, scoring a comical own goal. Joachim Low's side has conceded 12 times in his three caps.
Playing for Barca is an entirely different proposition to international friendlies and Champions League qualifiers, of course. While Gladbach has a proud history and strong rivalry with the likes of Bayer Leverkusen and Borussia Dortmund, nothing he has experienced can compare to the cauldron of El Clasico or the latter stages of the Champions League.
That said, the only way he will improve in big game situations is to play in critical matches and there is little doubt that he has all the ability to become one Germany's great goalkeepers. One of them, Oliver Kahn, is of the opinion that he could become one of the best ever.
"It is really interesting to see how consistent his performances are considering his age," the 2002 World Cup hero said. "Everything he does, he does with such calmness."
Arguably die Mannschaft's greatest ever keeper, Sepp Maier is also a vocal admirer. "Marc is virtually on a par with Manuel Neuer. Neuer has just preceded him. He plays for Bayern and has distinguished himself internationally."
Ter Stegen has responded to big challenges in the past - it can't be easy to come into a team sinking like a stone and lead them to survival, particularly as a teenager, but Barca's management and fans must have patience and build up his confidence.
His scope to grow is enormous and moving to Camp Nou will help him reach the next level, so his signing is a risk, but certainly one worth taking.