Fabian Delph believes Raheem Sterling has become one of the best players in the world at Manchester City.
The midfielder has hailed his club and international team-mate ahead of Thursday's Nations League semi-final with Holland in Guimaraes.
The pair are with England after winning the domestic treble with City, with Sterling scoring 25 goals and winning the PFA Young Player of the Year.
Delph joined City three days after Sterling moved from Liverpool in a deal worth up to #49million in 2015 and the former Aston Villa captain has seen his development first hand.
"He's an amazing young man, people forget he's only 24. When we both signed he was 19 (sic) and he looked like a little baby," said Delph, who has won two Premier League titles with Sterling.
"When he came to City he had three seasons under his belt and he's not that young in football terms but he's always had the mindset he will be one of the best players in the world.
"For the last four or five years he's never questioned himself and I've never questioned him.
"People always question what type of player he'd be and whether he'd go to the next level but I was like 'this kid has everything. Once he finds his path and what works for him you're going to see something incredible'.
"I believe he's operating at about 80 per cent so if he can push himself a little more - which he will because his mindset is very good - the sky's the limit.
"I'm speaking from knowing Raheem since he was 19 and seeing his progression. Right now he's one of the best players in the world."
Sterling will win his 50th England cap should he play, as expected, against Holland and Delph feels his colleague deserves to reach 100 caps.
"Yeah, I hope so, and there's a lot of young guys in the squad who could go on to get 100-plus caps, not just Raheem," said Delph, who has 18 caps.
"But from knowing him and what his mindset is like, I'm pretty sure that he's got that in the back of his mind that he wants to go and break that record or head towards it."
Delph, 29, retained his spot in the England squad despite starting just one Premier League game since Christmas.
He added: "It's frustrating for anyone who doesn't get as much time as they want. I'm quite experienced now, I'm very level-headed and my main focus was to help my team-mates.
"I always talk about being a team player, I'm a really good team player and I had the lads' back all the way through.
"It's always such a big deal for me to be selected for my country. Over the last 18 months we have been doing really well."