In retrospect, it seems crazy, but when I first trained with Sergio Aguero after he came to Manchester City in 2011, I didn't immediately think of Superstar.
Sometimes when a new player joins your club, you see him in action with your own eyes and just think "wow".
It happened a lot in City at the time because we made big signings that changed the club, but Sergio didn't. When I saw him for the first time, I didn't think he was that good.
We had spent a lot of money on him – about £ 35m – and he had arrived with a reputation, but he didn't look very special in the first few sessions.
It's not like I expected him to dribble past four or five players, but I marked him most of the time and he didn't really do anything.
He looked sluggish and was actually pretty lazy, to be honest. I wondered what all the hype was about.
I only knew how good he really was when he played his first game for us. He came to life in matches and everything about him was different.
In fact, I prepared his first goal for City in his debut against Swansea with a cross that he deflected on the long post – and he's obviously scored a few more since then.
Now when I look at his top-rated overseas player record in Premier League history, I wonder why I ever disregarded him.
His achievements are phenomenal and keep going.
Movement is only part of what makes Sergio so special
What is special about Sergio? Where do you start Everything about him is world class.
His movement when City attacks is just incredible. His game is not just about running away from the defenders, he can also get deeper to get the ball. In any case, he manages to find space if there is none.
Then there is his finishing. If the ball fell on him in front of the goal, I would support him every time to score.
This is partly because he is so calm when he has a chance, but also because he hits the ball so cleanly – put it all together and you have a deadly finisher, and everything is so natural to him ,
Some strikers see their goals dry up as they get older, but not Sergio. He is now 31, but has maintained his minutes-to-goal ratio for several seasons.
Yes, it helps that he is in town and playing for a team that creates many opportunities, but he has continued to work hard to ensure that his level has not dropped, even though he has sustained many injuries.
I would attribute this to Aguero's character, which is another important reason for his success.
When Pep Guardiola took command of City in 2016, Aguero didn't always play, but he responded just right.
While he might have shown his frustration on the field when he was replaced, Aguero has never publicly complained about anything.
I think that's only because he has always underpinned his own abilities. His approach seemed to be, "Well, you can play whoever you want, but if I can play again, I'll score."
He is also willing to listen, so he was able to adapt his game under Guardiola.
You saw another example of this in City's win over Aston Villa on Sunday. Of course Aguero got another hat trick, but you also saw him pull the ball back to prepare his team's second goal.
When I played with him, he was more of a finisher. The work ethic you see of him now is the one that Pep instills in him, and that's why he took his game to the next level, because now he's doing everything he did when I played with him, and more.
The medal that would make him one of the greatest players in football
When that moment comes, it will be almost impossible for City to replace Aguero.
His goal balance is just incredible, as is his attitude. For someone who's a real superstar, he's so humble – and he's the nicest man you'll ever meet.
Many superstars may be great talents on the pitch, but they can also be a bit difficult. At Aguero, both parts are just right.
Yes, he shows emotions like he did with Riyad Mahrez at half-time at Villa Park and asks him why he didn't go over to him when he was through, but it's always just about football.
When you talk to him, he just wants to play and score goals. That's what he's about, and I love that about him.
With his talent and attitude, it was inevitable that he had so much success in the Premier League, and of course he already has his historic moment here, because his goal, which won the title in 2012, will never be forgotten.
But when he leaves the club, I only hope that he also won a Champions League medal, because that's the only thing he lacks at club level.
Whether he wins or not, his legacy as the city's greatest striker or player reputation will not give up or break because he has already achieved so much. But it would get him exactly where he deserves it.
Can City triumph in Europe this year? Well, they're definitely good enough to win, and Aguero is just one of the reasons.
I'm worried that teams like Real Madrid and Paris St-Germain – to name just two – are also world-class strikers.
Sometimes when I see City playing because they are so expansive and play with such freedom, they can't help but leave gaps.
You can't afford to do that now that you're in the knockout phase, where a bad half can be enough to take you out, and defensive must be more solid if you want to go all the way.
Micah Richards spoke to Chris Bevan from BBC Sport.