Alexander-Arnold’s inclusion in England’s Euro 2020 squad as one of four right-backs was a major talking point – but his tournament could be in doubt after he hurt himself making a late clearance.
“It’s not a good situation that he’s had to walk off in some discomfort,” Southgate told BBC Radio 5 Live.
“We’ll know more details in the next 24 to 48 hours. It looks like a thigh injury – in terms of the full extent, we don’t know yet.
“It’s devastating, he’s worked hard to earn a spot here. I just hope it’s not too serious.”
Southgate did not want to be pressed on who would replace the 22-year-old Liverpool player in his 26-man squad if he has to pull out.
“Let’s see how Trent is and then we’ll go from there,” he told ITV.
Southgate revealed there were other fitness problems too.
“Jadon Sancho has been ill and was ruled out and with Kalvin Phillips we had already made a decision that although the shoulder was progressing well we were going to wait until Sunday before putting him back into the game,” he said.
“That’s why we ended up with 10 and then nine at one point and two with cramp, so the end was a bit of a mess.
“Declan Rice has missed a bit of training this week, you can see that one or two are physically a bit short.”
