The Burnley man sat alongside Southgate for the Three Lions' pre-match press conference ahead of winning what will be his fourth cap.
And Southgate was glowing in his praise for the stopper, who is behind Jordan Pickford in the pecking order to be England's number-one goalkeeper.
"Nick has been, first and foremost, a fantastic part of why the squad has progressed and had a reasonable amount of success comparative to what England have done over the years," enthused the Three Lions boss.
"He's been an incredible member of the squad – high performance level, low maintenance in terms of neediness and sacrifices himself for the team at all moments. You couldn't ask for a better person to have in the group."
Southgate continued: "He's had to be so patient to get game time and we feel it's important he's getting that – last month (versus Wales), this month and the game in Kosovo (in November 2019) – because I recognise how difficult it is to travel as one of the goalkeepers who isn't starting all of the time. That's tough – a lot of goalkeepers have retired from that over the years and I totally understand it.
"We're hugely appreciative of having a goalkeeper of Nick's quality who, at the moment, is just behind Jordan but absolutely that fight is there, that push is there.
"He's got a great habit of keeping the ball out of the net – that's a bit old-fashioned in terms of what people want from goalkeepers. They want them to start attacks, create attacks, juggle, do all sorts of things but there's something to be said for coming and collecting crosses, dominating your box and keeping the ball out of your net with good saves, and he does that.
"We couldn't be happier with him as a guy to work with."
And the England manager hinted that the 25 year old could have a big part to play in this month's matches, with Thursday's game being quickly followed by UEFA Nations League fixtures against Belgium and Iceland.
"We've got three matches and it's quite possible that he could start in any of those three," Southgate confirmed. "For sure he's going to play an important role for us in this camp.
"He's playing extremely well. I've talked a lot to Jack about end product. In the last 22 games of last season, he [scored] one goal and now he's four goals in seven Premier League games – five in all competitions – and his assists are high.
"When we talked at the end of last season about the likes of Raheem [Sterling], Marcus [Rashford] – 20 goals plus. Jack is hitting those figures this season, and that's a great step forward. We know his all-round game has always been good but to hit those numbers when you're an attacking player is really important.
"He's doing that well, and his work without the ball is really improving as well – his pressing, his discipline on his defending – so I couldn't be happier with what he's doing. It's a really good moment for him and for sure he's going to play a big part for us this week."
Southgate also defended his decision to draft 17-year-old Jude Bellingham into his squad, with the Borussia Dortmund midfielder in line to become England's third-youngest-ever player if he makes his debut this month.
The manager explained: "It's always interesting to see the reaction when we select a player, because people are immediately talking about other players without understanding why we've called Jude up.
"We could flippantly say 'well, he's playing for a massive club' and 'he's playing Champions League football' but there's actually a bit more to it than that. Positionally, he's playing in a two-man midfield at Dortmund, whether that's a 4-2-3-1 or a 3-4-3, so he's in the exact position that we lost a player in James Ward-Prowse.
"But the bigger picture here is that we're giving a young player an opportunity to work with us, to spend some time with us and invest some time in him. He'll have a brilliant experience for a few days and if we can get him on the pitch and get some match minutes as well that'll be a bonus.
"We think it's part of what we've done over a long period of time in developing young players – that's the approach we've taken to this England squad and we think it's served us well. It's helped give young players experience that will benefit England in the long term.
"It's not a decision that he's a better player than one or two older players who I've seen mentioned – although those players don't play in the position that he plays and that's a fact. People will have a view of what a midfield player is but there are very specific roles within midfield positions.
"The bigger picture here is the opportunity to bring another young player with us that is going to benefit England for the long term."
England take on the Republic of Ireland at 8pm on Thursday night, with the match live on ITV.