South Korea coach Shin Tae-Yong says he is pleased with the form of Tottenham striker Son Heung-Min but is concerned about potential burnout heading into the World Cup in Russia this summer.
Son scored two goals in a 4-1 win against Bournemouth on Sunday, taking his tally to seven goals in his last four games in all competitions, and he was selected for South Korea's World Cup squad on Monday.
"I hope Son can perform in the World Cup like he currently does for his club, but I'm concerned that Son's red-hot form could cool down around the World Cup period," Shin said at a news conference in Seoul.
"No player can maintain his best form all season long. I'm really worried that Son's form might go down from May, with his concentration waning and him becoming physically fatigued."
Son will feature in South Korea's friendlies against Northern Ireland in Belfast on March 24 and Poland in Chorzow four days later.
Shin called up five European-based players, with Son joining Swansea City's Ki Sung-Yueng, Dijon's Kwon Chang-Hoon, Augsburg's Koo Ja-Cheol and Red Bull Salzburg's Hwan Hee-Chan.
South Korea face Germany, Mexico and Sweden in the World Cup, which begins on June 14.