The 21-year-old endured a nightmare Nerazzurri debut, but his new coach was happy with the bottle the forward displayed in taking on the responsibility of a second spot kick
The Nerazzurri cruised to a 3-0 win over a Trentino select side on Wednesday, with Rodrigo Palacio, Alessandro Capello and Ricky Alvarez all on target.
However, it was Belfodil who made the headlines for twice failing to convert from the penalty spot on his Inter debut.
"When there are games that count, I will decide penalty takers," Mazzarri told reporters after the friendly win.
"Belfodil has failed twice, but it changes little and anyway, he showed personality because after missing the first one, he returned to the penalty spot."
Inter also failed to impress overall, but Mazzarri insisted that he was not in the least bit surprised by their uninspiring performance.
“I already knew we would struggle,” he claimed. “You can tell when the muscles haven't loosened up properly yet.
“In the first half their legs weren't really firing, then it got better. I'm pleased with how things are coming along though.
“Considering the workload we've put them through they're doing great. You can see that they're still a bit leggy but we're working on it.
“The friendly performance has to be put into perspective. However, we'll look to learn from everything.”
Mazzarri only arrived at Appiano Gentile this summer, after a successful four-year spell in charge of Serie A rivals Napoli.