But the midfielder confirmed he had picked up an injury in the first-half and told reporters after the game: "Hopefully I'm OK. It's my quad."
The England coaching staff will assess the injury upon the team's return to the base in Repino, with Alli hoping it will not rule him out of Sunday's clash against Panama.
Southgate insisted the England coaching team were keeping an eye on the Alli throughout the game.
"We had to keep monitoring Dele," Southgate said.
"He was feeling a little bit of an issue just before half-time, but he felt he could carry on and I thought the runs that he was making and the way he was pressing the ball was still causing a problem.
"He had a half chance with a lovely ball Jordan Henderson played to him, lofted over the top.
"But we have good options on the bench and we felt to put the freshness of Marcus (Rashford) and Ruben (Loftus-Cheek) would both bring fresh energy but also a different sort threat to the one that we'd posed."
The Three Lions won their opening match against Tunisia after England talisman Harry Kane netted a double on his tournament debut.
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