Hailing from Guangdong, Yuan can speak Cantonese, a dialect Su tends to use when communicating with his family and local peers.

The pair hit it off instantly. Su improved his 100m PB to 10.45 in 2007 and improved it with 10.41 the following year while still a junior.

In 2009 he established himself as an elite sprinter in Asia, winning 11 national and international races over 60m, 100m and the 4x100m.

The first big highlight of Su's career came in 2011 when he clocked 10.16 to win at the National Championships, breaking the national record of 10.17 which had stood for 13 years.

After that, Su continued to make history.

He clocked 10.19 at the 2012 Olympics to become the first Chinese to reach the semi-finals of the men's 100m at the Games. In 2014 he became the first Chinese sprinter to reach the final of a global senior championship, finishing fourth at the IAAF World Indoor Championships in Sopot, Poland.

More recently, on 30 May this year, Su sprinted to a national record of 9.99 to become the first Chinese athlete to dip under the 10-second barrier.

"9.99 is like a landmark for China," said Su. "As a Chinese person, I feel so proud to make history like this. But I am not going to be complacent with this result; I still have a long way to go and need to keep working hard in the future".

In the eyes of Yuan, Su's breakthrough came after years of hard work.

"Su is the kind of athlete who, once he has set himself a goal, he will devote himself entirely to achieve it," said Yuan.

"He improved his PB to 10.06 at the IAAF World Challenge meeting in Beijing in 2013. Since then, he set his goal to run under 10 seconds and Zhang Peimeng's 10.00 national record at the World Championships in Moscow gave him more courage; it convinced him that a sub-10 run was not an impossible mission for Chinese athletes."

Two years ago in Moscow, Zhang missed out on the 100m final by mere thousandths of a second. Su, meanwhile, was disqualified from his semi-final for a false start.

At the IAAF World Championships, Beijing 2015 later this summer, Su hopes to gain redemption by becoming the first Chinese athlete to make it to a 100m final at the IAAF World Championships.