Kagawa and CSKA Moscow playmaker Keisuke Honda in a 23-man squad including 11 Europe-based players for the home friendlies.
Japan play Guatemala in Osaka on September 6 and Ghana in Yokohama four days later.
"As a matter of course, I have expectations for the new players," Zaccheroni said. "I will prod the team to grow as one and become more united through the two matches."
One of the four strikers is Cerezo Osaka's Yoichiro Kakitani, 23, who made his senior international debut at the East Asian Cup in South Korea, where he won the golden boot with three goals as Japan roared on with two wins and one draw.
The others, all also aged 23, are Manabu Saito (Yokohama Marinos), Masato Kudo (Kashiwa Reysol) and Yuya Osako (Kashima Antlers). They scored a total of four goals at the regional tournament.
"I am looking forward to seeing how Osako and Saito blend with the first-team regulars. They have played remarkably well in the J-League and kept developing themselves. That is why I thought they deserved this chance."
Kakitani also played in full-strength Japan's 4-2 defeat at home to Uruguay two weeks ago.
Zaccheroni, who coached several Serie-A clubs before taking over the Blue Samurai, needs to strengthen their defence after they yielded nine goals in three group matches at the Confederations Cup in Brazil in June.
Japan, who became the first country to qualify for the 2014 World Cup finals, lost to Italy, Brazil and Mexico at the tournament of continental champions.
But the Italian tactician kept faith with his first-choice centre backs, Maya Yoshida of Southampton and Yasuyuki Konno of Gamba Osaka.
Inter-Milan's Yuto Nagatomo and Atsuto Uchida of Schalke were called up as full backs as usual.
Goalkeepers: Eiji Kawashima (Standard Liege/BEL), Shusaku Nishikawa (Sanfrecce Hiroshima), Shuichi Gonda (FC Tokyo)
Defenders: Yasuyuki Konno (Gamba Osaka), Masahiko Inoha (Jubilo Iwata), Yuto Nagatomo (Inter Milan/ITA), Masato Morishige (FC Tokyo), Atsuto Uchida (Schalke/GER), Maya Yoshida (Southampton/ENG), Hiroki Sakai (Hannover/GER), Gotoku Sakai (Stuttgart/GER)
Midfielders: Yasuhito Endo (Gamba Osaka), Makoto Hasebe (Wolfsburg/GER), Toshihiro Aoyama (Sanfrecce Hiroshima), Keisuke Honda (CSKA Moscow/RUS), Hiroshi Kiyotake (Nuremberg/GER), Hotaru Yamaguchi (Cerezo Osaka)
Forwards: Shinji Okazaki (Mainz/GER), Shinji Kagawa (Manchester United/ENG), Yoichiro Kakitani (Cerezo Osaka), Manabu Saito (Yokohama Marinos), Masato Kudo (Kashiwa Reysol), Yuya Osako (Kashima Antlers)