Mashaba said he omitted Serero from the 23-strong group because "other players were better than him."
South Africa have qualified for the Cup of Nations for the first time since 2008.
Since taking over the Bafana Bafana reins in July, Mashaba has restored pride to a national team that steadily slumped after conquering Africa in 1996, while also lifting morale when goalkeeper-captain Senzo Meyiwa was murdered during the qualifying campaign.
The central African country stepped in to host the continent's most prestigious tournament after Morocco backed out due to fears over Ebola, which has ravaged some west African countries and killed 7,842 people out of 20,081 cases.
Goalkeepers: Darren Keet (Kortrijk/BEL), Brilliant Khuzwayo (Kaizer Chiefs), Jackson Mabokgwane (Black Aces)
Defenders: Thabo Matlaba (Orlando Pirates), Patrick Phungwayo (Orlando Pirates), Thulani Hlatswayo (Wits), Siyabonga Nhlapo (Wits), Rivaldo Coetzee (Ajax Cape Town), Eric Mathoho (Chiefs), Anele Ngcongca (Genk/BEL)
Midfielders: Bongani Zungu (Sundowns), Themba Zwane (Sundowns), Reneilwe Letsholonyane (Chiefs), Mandla Masango (Chiefs), Dean Furman (Doncaster/ENG), Andile Jali (Ostend/BEL), Oupa Manyisa (Pirates), Thuso Phala (SuperSport), Thamsanqa Sangweni (Chippa)
Strikers: Bongani Ndulula (AmaZulu), Tokelo Rantie (Bournemouth/ENG), Bernard Parker (Chiefs), Sibusiso Vilakazi (Wits)