Reflecting on Tuncay's winner against Derby on Saturday, Southgate declared: "A couple of weeks ago he wouldn't even have attempted that.
"He would have tried to control the ball and then have a go. But the form he's in now he'll take a chance and he got his reward. It took him a while to settle in. He wasn't used to the physical demands of this league and is just learning the language.
"In their league, there were probably eight or 10 hard games a season and the others were pretty routine. Tuncay is a superstar in Turkey because of what he did at Fenerbahce. He was the King of Istanbul and sometimes that makes it more difficult to adjust.
"But he is very fit and very fast and, at just 25, you suspect he is going to get better and better for us."