Olympic hero and former 400m world record holder Michael Johnson believes it will be “very difficult” for Wayde van Niekerk , the current 400m world record holder, to defend his crown at the 2020 Tokyo Olympics.In one of the greatest South African sporting moments of all time, Van Niekerk shattered Johnson’s long-standing record at the 2016 Rio Olympics with a time of 43.03 seconds that stunned the world and catapulted him to global superstardom.The darling of South African sport with the brightest of futures, Van Niekerk then sustained a freak knee injury while playing in a celebrity tag rugby match at Newlands in September 2017.ALSO READ: Wayde returns with 100m winIt would prove to be catastrophic for the then-25-year-old, who tore his ACL in a moment that would prove to be career-threatening.Van Niekerk has not competed internationally since the injury, despite having won at the 2019 Free State Championships in February of that year.He won an unofficial 100m meet in Bloemfontein on Monday night and is understood to be on track to compete in Tokyo.Johnson, who had held the world record of 43.18 seconds since 1999, believes that South Africans should approach Van Niekerk’s efforts at the 2020 Olympics with a realistic level of expectation.“I hope that he can get back and that he’s there. The problem is that, if he’s there, it’s going to be very difficult for him to be at his best,” said Johnson at the 2020 Laureus World Sports Awards in Berlin.“The more time you have off away from the sport, and now he’s missed two seasons, the harder it gets and it technically would take maybe one season to get back into race shape.“I think the expectation for what he will be able to deliver if he is there should probably be tempered.”Johnson acknowledged, however, that Van Niekerk had already proved that he was not a regular athlete after achieving what he did in 2016.“People approach the sport differently from a mental standpoint. Everyone is different in terms of what they’re able to overcome and how they’re able to deal with the pressures of performance and expectation,” he said.“Obviously, mentally it’s tough to come back after two years and in an Olympic year and when so many others are running really fast.“But everyone is different and it takes a different person to become Olympic champion, world champion and world record holder. That’s a different type of athlete who many may not see as human.“It’s not to say Wayde doesn’t stand any chance. He is a different type of athlete, so he may not take the same pattern as everyone else. We’ll just have to see.”After the 2016 Olympics and before the injury, there was significant global talk around whether Van Niekerk could become the first man in history to dip below 43 seconds over 400 metres.“Before the injury, after his 43.03, I would have said ‘yes’,” Johnson said when asked if he still thought that possible.“You’ve got to be right at the right time when everything comes together and those opportunities are rare. He’s at the point now where, realistically, it is going to be difficult.”The 2020 Tokyo Olympics get underway in July.For more sport your way, download The Citizen’s app for iOS and Android.