[8][9] However, confusion regarding how agents work in European football caused him to miss out on the trial;[10] furthermore, his club Ulsan had already agreed to a contract-binding deal to sell him to Yokohama F.

[12] Following his success at the 2002 FIFA World Cup, there was interest from many major European football clubs, and he nearly signed a deal with Tottenham Hotspur, to the point that he had already said farewell to Kashiwa; but the negotiation broke down.

[10] Without a club, he returned to Ulsan after the registration deadline and was granted a special exemption to play with the team.

[10] With only eight matches left in the 2002 season, he scored nine goals, helping Ulsan move from a mid-table position to a title challenge, finishing in second place.

[17] He was also part of the South Korea under-23 team for the 2004 Summer Olympics,[18][19] who finished second in Group A, making it through to the next round, before being defeated by Paraguay, the eventual silver medalists.

He was originally a defensive player, who could perform roles of stopper and right back with excellent physical strength, but he had the ability to spark attacks with his incisive distribution after getting great positioning and wide vision in his experiences.

His tenure at Jeonnam Dragons ended on August 16, 2018, when he resigned after only three victories, with the team doing poorly in the 2018 K League 1 standings.

Despite the diagnosis, he continued to manage Incheon United and helped the club avoid relegation, before resigning in January 2020.

In June 2020, when Incheon United had another managerial vacancy, Yoo approached the team and asked to be appointed the manager again, but he was turned down on account of his poor health.