China shot to the top of the Olympic medal table for a large part of Day 2, thanks to golds from weightlifter Long Qingquan, shooter Zhang Mengxue and the synchronized diving pair of Wu Minxia and Shi Tingmao.

But away from the sporting action, one controversy in particular has threatened to erupt into full-blown diplomatic incident.

Mack Horton, the Australian swimmer who beat China's Sun Yang in the 400-meter freestyle, doubled down on his previous comments that Sun, who served a 3-month doping ban in 2014, should not be competing at the Games, again referring to him as a "drug cheat" as the pair jointly addressed ­media.

Chinese Net users have flooded ­Horton's social media accounts, demanding an apology, while Sun later told Australian media that Horton was no friend of his, contradicting the ­rather hollow claim by Chinese swimming team manager Xu Qi that Sun was close with many in the Australian team.

Unfortunately, no one is emerging with much credit in this sorry saga.

Horton, 20, is entitled to his opinion - and has been backed by the Australian Olympic Committee - and is no doubt voicing what many of his teammates think. But the fact that several Australian swimmers, at least one of whom is now in Rio, have previously been caught taking banned substances rather undermines his stance.

Sun is also far from blameless in this war of words. He reportedly taunted Horton in the training pool by splashing him and was later pictured on the bus back to the village smirking at ­Horton's teammates, who were clearly not amused.

Chinese fans, disappointed that Sun lost out in the final and then spurred on by emotional footage of his tears after the race, have jumped to defend their hero's honor, but attacking Horton ­online and making death threats against Australian reporters hardly covers China in glory.

Meanwhile, Horton's needling ­comments and deliberate attempts to unsettle Sun, while classless, are all part of the game.

But arguably the biggest blame lies with China's swimming authorities.

The fact is that Sun did serve a doping ban for failing a test and, whatever the circumstances surrounding that suspension, the mishandling of the incident - with the ban only announced after it had been completed - gave the appearance of a coverup.

Given the heightened sensitivity of doping issues today, this has arguably condemned Sun's achievements to be tainted for the rest of his career.

Love him or hate him, though, Sun Yang has been rattled and must now sharpen his focus if he is to get revenge in the 1,500-meter freestyle later this week.

Mark Dreyer is the editor of China Sports Insider. A former reporter at Sky Sports and Fox Sports, he regularly comments on China's sports industry in global media. dreyermark@gmail.com