"There is big competition, a lot of quality in the squad," said Maddison.
"You have to make sure when you are called upon, you do the business. I don't lack the confidence and belief in myself to do that. I just want that opportunity, I want that time on the pitch, because I know what I'm capable of. I know my quality can help this team, most definitely. I show what I have in training every day. The manager sees it.
"You've also got to show it, and you've also got to have the opportunity to show it. I didn't feature in the first game, which was disappointing. Watching on the side (against Belgium), I could see there was quite a lot of space between the lines, where I like to play, so I was thinking, 'Come on, Gareththere's a lot of space!'."
Maddison insists he can complement Phil Foden and Jude Bellingham.
"I kind of wanted to go on with them players, not replace one of them, which is what actually happened," he added.
"Kobbie played outstandingly. I probably bring a different sort of profile, so I wanted the Bellinghams and Fodens still on the pitch. I came on and we linked up well and were creating and managed to get the goal in the end.
"It's not the be-all and end-all that I got an assist. But I came on and made an impact. I'm showing him (Southgate) what I'm capable of and I just want to show more of that.
'Jude went a bit deeper. Phil is very strong off the left and the right and can drift. It's not like we're all stood in a line in the middle!
"I think it worked really well. I could see the spaces in there. If you've got clever players, top players with good awareness, you don't really get in each other's way as long as you've got the right patterns. A couple of times I went a little bit deeper and was passing to Phil in the number 10 position. We all went in different positions."