The 30-year-old Marchisio was left out as a precautionary measure so that he can rest a left leg injury, the Italian FA said on Monday in a statement on their website. (www.figc.it)
Marchisio, capped 54 times, returned to Serie A side Juventus last month after spending six months recovering from a cruciate ligament injury in his left knee.
Medical tests confirmed Napoli striker Gabbiadini was carrying a slight injury sustained during Napoli's 1-1 draw with Lazio on Saturday.
Ventura called up uncapped duo, Atalanta midfielder Roberto Gagliardini and Genoa defender Armando Izzo, as possible replacements for Marchisio in the two matches.
AC Milan forward Gianluca Lapadula, last season's Serie B top scorer, has also been called up for the first time in place of Gabbiadini.
Juventus defender Andrea Barzagli will be out of action for about two months after sustaining a shoulder injury in the 2-1 win at Chievo in Serie A on Sunday.
"The defender's arm will be in a sling for the next four weeks with a return to action scheduled for approximately two months' time," the Italian champions said on Monday.
The 35-year-old will be replaced in the Italy squad by Fiorentina defender Davide Astori.
Italy are level on seven points behind group leaders Spain after three games.
(Reporting by Silvia Recchimuzzi in Gdynia; editing by Mark Heinrich and Pritha Sarkar)
