He scored all four of Chelsea’s goals in the group stage win against Sevilla - and with Wednesday’s game being played in the neutral venue of Seville, Tuchel had hinted he could be in line for a start.
However, Timo Werner leads the line instead, supported by Kai Havertz.
“He’s in the running, he’s in the squad, and he’s absolutely excited to return to Sevilla, to play there, it gives him a good feeling,” Tuchel had said of Giroud.
“And he’s very strong for us in the Champions League, he has history in Sevilla, scoring many goals in this campaign. So obviously he’s in the running.”
Chelsea have also been boosted by the availability of N’Golo Kante, who is on the bench alongside Christian Pulisic, Tammy Abraham and Thiago Silva.
Antonio Rudiger starts after his training ground bust-up with Kepa Arrizabalaga, who is on the bench.
Chelsea XI: Mendy; Azpilicueta, Christensen, Rudiger; James, Jorginho, Kovacic, Chilwell; Mount, Havertz, Werner
Subs: Kepa, Caballero, Thiago Silva, Zouma, Alonso, Emerson, Kante, Hudson-Odoi, Ziyech, Giroud, Abraham, Pulisic
Porto XI: Marchesin, Manafa, Mbemba, Pepe, Sanusi, Corona, Grujic, Uribe, Otavio, Marega, Diaz
Subs: Diogo Leite, N'Diaye, Claudio Ramos, Baro, Joao Mario, Felipe Anderson, Martinez, Evanilson, Nanu, Sarr, Vieira, Francisco Conceicao