Chelsea defeated Inter in the US last week.
"Inter have revealed themselves to be a team it is tactically not easy to play against,” Mourinho told La Gazzetta dello Sport.
“It was a shame Hugo Campagnaro was sent off, as playing 11 against 10 was not useful for me or Mazzarri.
“I now know Mazzarri well enough to say he can give Inter what they need now: a clear path and a precise idea to begin from.
“I cannot judge what qualities Inter have today, but at least that is something I can say with certainty.”