Former South Korean football star Park Ji-Sung has lamented a lack of unity in the national team as it struggles to qualify for the World Cup.
The Taeguk Warriors have reached eight World Cups on the trot, but are in danger of missing out on direct entry to Russia 2018 after a string of poor results, including defeats to China, Iran and Qatar.
"People say players tend to be (too) easy-going or divided into different factions but it's difficult to place the finger of blame on just one problem. Every little problem adds up to big trouble," the Korea Times quoted Manchester United veteran Park as saying.
"The most important thing is that the players must trust each other."
German coach Uli Stielike was sacked in June and succeeded by Shin Tae-Yong, a former midfielder for Seongnam Ilhwa Chunma and Brisbane Roar.
But whether the players were ready to make changes on the pitch was key, Park said.
It was "clearly wrong" for players to talk back when rebuked by coaches or captain, Park said.
"There certainly exist red lines that should not be breached by athletes."
Park -- a key member of the South Korean side that reached the World Cup semi-finals on home soil in 2002 -- gave the current team a 50 percent chance of getting to Russia from Group A.
South Korea are clinging to the last direct qualifying spot with two tough games to go -- at home to group winners Iran on August 31, and away to rival contenders Uzbekistan on September 5.
"Playing against two strong teams is a blessing in disguise for South Korea as it gives players extra motivation," Park said.
"I think South Korea could make it by defeating Iran at home and collecting a draw against Uzbekistan."