Hernanes joined the Nerazzurri from Lazio in a big-money deal in January and is in line to make his debut against strugglers Sassuolo on Sunday.
Inter have failed to win a game in 2014 and were comfortable beaten 3-1 by leaders Juventus last week but Mazzarri believes his new midfielder could help the likes of Mateo Kovacic to improve in the latter part of the campaign.
"I hope Hernanes can do even more than he has done so far in his career," he told a press conference. "He's a Brazil international and can help Mateo Kovacic to grow too.
"We needed a player with extreme quality who can also help those with less experience. I don't want to give him too much responsibility but he can be useful psychologically as well."
Mazzarri has come under pressure recently following a run of five league games without a win that has seen Inter drop to sixth in Serie A.
However, Inter president Erick Thohir insisted on Tuesday that the former Napoli boss will form part of the club's future plans, and the 52-year-old was delighted with the owner's public backing.
"I already knew what he [Thohir] thought but it's important for what we're doing here that the president said certain things publicly as well," he said.
"Words of praise like that carry a lot of meaning. Now I only hope that we can turn around this negative run of form we're in as soon as possible.
"We're working well in training, both mentally and physically.
"Right now the result is more important than anything else. It's important for the players so that they can feel freer again because negative results start to weigh down on you."