Raheem Sterling still has plenty of improvement to come, according to Fabian Delph – and his Manchester City and England team-mate will not be shy in letting him know about it.
Sterling was a standout performer as Pep Guardiola's side won an unprecedented domestic treble this season, scooping the Football Writers' Association (FWA) Footballer of the Year award.
A brace in the 6-0 FA Cup demolition of Watford took the 24-year-old to 25 goals in all competitions for his club in 2018-19, a campaign where he also emphatically turned a corner at international level.
Despite his best efforts, Sterling's England goal drought remained stubbornly intact throughout the run to the semi-finals of the 2018 World Cup.
He has since scored six times in five starts for the Three Lions, including a Wembley hat-trick in a 5-0 Euro 2020 qualification thrashing of the Czech Republic.
As doubts over Harry Kane's match fitness persist, Sterling indisputably approaches what will be his 50th England cap in Thursday's Nations League Finals encounter against Netherlands in Guimaraes as Gareth Southgate's most important and potent attacking threat.
"When we both signed he was 19 and he looked like a little baby," said Delph, who joined City from Aston Villa during the same 2015 close-season when Sterling secured his exit from Liverpool.
"People always questioned 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 think the sky's the limit. Right now, he's one of the best players in the world. And while I'm still with him, or while I'm still in contact with him, I'm going to be pushing him daily because I know he's got another 20 per cent in him."
It was also a season where Sterling's articulate and impressive response to suffering racist abuse placed him at the forefront of football's fight to tackle a sickening stain on the game.
Superb performances continued unchecked and Delph identifies a level of mental strength virtually unparalleled in his experience.
"He's got the strongest mindset I've ever come across in football," the 29-year-old midfielder said. "Vincent Kompany is another one, he is very strong mentally.
"Nothing fazes Raheem, he is very confident in himself. He's a great person and very dedicated to his craft. I've watched him mature a lot over the years, he's still the same guy who I met when he was 19.
"The only difference is people are paying attention to what type of person he is and trying to know Raheem a little more. Everyone can see how kind and humble and what a good player he is."
Delph is unable to match Sterling's tale of personal success at City this season, having found first-team opportunities scarce since the turn of the year.
Southgate made him captain for England's friendly against the United States last November and he retains his place in the squad as an influential dressing-room presence – something a lack of game time at club level has not tempered.
"I can be very emotional, so when it's the build-up to a game, I enjoy that side of trying to help push the team and get them fired up," Delph, whose behind-the-scenes rants made him a star of City's 'All or Nothing' Amazon documentary last year, explained.
"I've always been the same at City. To be fair, I was a nightmare when I was 18, 19 – an absolute nightmare. Six stone wet through and screaming at big ugly centre-halves."
He added: "The second half of the season I never played. But every time it's a home game and I'm there, I'm ranting and raving and speaking to people one-to-one, effing and jeffing, getting the team going. It's the way I've always been and will probably never change."