Inler recently suffered the heartbreak of failing to make next summer's European Championship, after Switzerland finished third in Group G behind England and Montenegro.
And Lamberti reveals the combative midfielder is hoping to make up for the disappointment with the national team by helping his club side to success.
"Gokhan really wanted to take part in the European Championship," Lamberti to Marte Sport Live.
"He is disappointed and there is some bitterness but he now has to focus on other things.
"He'll make up for the failure by winning with Napoli.
"He loves this city and he's sure he has made the right choice in moving here."
Inler spent much of last season being linked with a move to Juventus, but it was Napoli that sealed his services from Udinese earlier this summer for a fee of €13million.
Since moving to the Stadio San Paolo, Inler has slotted seamlessly into the first team and has helped Napoli to three wins in their first five Serie A games of the season.