Southgate has often left it until late into games to make substitutions – apart from some made at half-time – but he said changes are “not pre-conditioned” and depend on the game.
“You are always looking at the freshness of the team and the balance of the team and whether changes are going to make an improvement to the team or not,” he said.
“The game will take us in a certain direction that will make that decision for us.”
Defender Luke Shaw made his first appearance from the bench in the win against Switzerland after returning from injury, but Southgate did not shed any more light on whether he will start Wednesday’s game.
The manager said they “have to decide” if Shaw, who had been injured for four months, is “ready to start”.
Southgate also dismissed concerns over a German referee once criticised over his match-fixing past by Jude Bellingham officiating the game.
Bellingham, then playing for Borussia Dortmund, was fined 40,000 euros (£34,000) in 2021 for referencing Felix Zwayer’s previous six-month ban for match fixing.
Southgate added: “I have no concerns about who the referee is, he will be at a very high standard because that is how Uefa make those decisions. It’s not even a consideration.”