Parker hadn't been in the ring for six months, since he dismantled Afa Tatupu in October, and yesterday's bout marked the first time he had the opportunity to show off his immense talent on such a big stage.
There was a worldwide television audience and plenty of movers and shakers in attendance, which all added up to a big night out for Parker.
There were certainly some jitters as the occasion got to him slightly, but ultimately he moved to 8-0 with seven knockouts for his professional career.
"I thought it was a fight where Joseph learned more than he has in his previous seven fights," Barry said.
"When he landed that right in the first round, if he had ended the fight then, I think we'd have learned nothing."
Nascimento enjoyed a good run in the sixth round when he landed a booming right to Parker's ear and also opened up a small cut above the 22-year-old's left eye.
Parker suffered a suspected perforated eardrum from the blow and was due to be checked out thoroughly by a doctor overnight.
Parker was cut severely in his last bout when he clashed heads with Tatupu but that gash was in a different spot from the nick he suffered yesterday.
"The German doctor came in and put one stitch in the cut," Barry said. "It's very small. It won't interrupt our planning for July. I really don't believe it's going to be a problem moving forward."
Barry's reference to July is when Parker will fight next with a bout scheduled for Auckland against an opponent who will be confirmed shortly.
Parker's victory over Nascimento earned him the interim PABA heavyweight title and probably moved him to No15 in the WBA's rankings.
Barry said Parker's next opponent would be a challenge for him and there were ongoing discussions with promoters Duco about managing everyone's expectations.
"Joseph is in the very early, apprenticeship stages of his professional career," Barry said.
"Our promoters are far more aggressive with wanting Joseph moved up the rankings; faster than myself. But the opponent we are talking about for July is someone who I think is going to be a nice test for Joseph."
Barry and his team set high standards for Parker and the heavyweight prospect knows he missed the mark in certain areas against Nascimento as he looked too keen to fire a knockout blow early on.
"People say it was a good knockout but I've got to get back to the gym and work on a few things," Parker said.
"But it was a great experience fighting on a big card."
Round by round recap
Round 1: After picking his spots early, Parker landed a sweet right hook late in the frame but Nascimento was able to get to his feet in time. Just.
Round 2: Parker looked to capitalise on his early dominance and finish the bout but he was unable to hit a big shot, although he still comfortably won the round.
Round 3: Parker continued to work the body, which was part of his fight plan but he looked slightly impatient in searching for a knockout.
Round 4: The South Aucklander's dominance began to show and Nascimento ate a huge left hook late in the round but managed to stay on his feet.
Round 5: This was the most even round of the fight, although Parker would have edged it on the scorecards. The crowd started to get in to it here.
Round 6: Parker made one slight mistake and Nascimento landed a big shot to Parker's ear. He also gave him a nick near his eye which later required a stitch. Nascimento's round.
Round 7: Parker came out with a roar and delivered a collection of stinging blows mid-way through the round. When Nascimento was unable to defend himself, referee Brad Vocale stopped the bout.
Daniel Richardson travelled to Germany courtesy of Duco Events.
