The Three Lions take on their World Cup semi-final conquerors in Rijeka on Friday, with both teams searching for their first win in League A Group Four.
Injuries to back-up goalkeeper Alex McCarthy and first-choice left-back Danny Rose have further complicated matters.
Southgate insisted he will field a team ready for the pressure of facing Croatia, but noted he thinks his whole squad has the quality to start.
"We're here to try and get a result so the team we play will be a team we believe in and [one that is] ready to start," Southgate told a news conference.
"Nobody in the squad is someone we're not thinking of putting into team, so it is not experimental, they are players we believe in.
"There are some players who are relatively inexperienced but who have impressed us in training and showed they can handle this level.
"The Croatia team is very strong. Mateo Kovacic was on the bench for the semi-final final but Ante Rebic and Ivan Perisic are two great attacking players.
"The midfield is almost the strongest in the world. It is a really good test for our team."
Rijeka pic.twitter.com/Kwviipp1Pz— England (@England) October 11, 2018
Friday's encounter at Stadion HNK Rijeka will be played behind closed doors, with Croatia serving their second game of a crowd ban imposed by UEFA after a swastika symbol became clear on the pitch during a Euro 2016 qualifier against Italy.
Southgate, whose side lost 2-1 to Spain in their first Nations League outing, is expecting a surreal experience, but insisted his players are well prepared.
"It will be strange, we effectively do that every day of our lives playing in front of a handful of people watching but for an international it is very different," he said.
"But we will be prepared. Croatia, I am sure will feel the same, not having the support of the passionate fans.
"It is a shame for the travelling fans who were brilliant for us at the World Cup and those who have not missed a game for decades."