Busan Daewoo Royals In 1998, Ahn started his professional career at
K League club
Busan Daewoo Royals. He was selected as one of the
K League Best XI that year after showing great performance as soon as he went there. Ahn made 30 appearances including 13 starts and scored five goals over two seasons. His time at Perugia was marked by his performance at the
2002 FIFA World Cup, where he scored a crucial golden goal in the round of 16 against Italy, leading to their elimination. The following day, Perugia's owner
Luciano Gaucci controversially terminated Ahn's contract, citing his goal as the reason and making xenophobic remarks about Ahn and the Korean nation. This decision was widely condemned as discriminatory and sparked a global outcry. Gaucci later retracted his decision and approved an option to sign Ahn on a permanent basis, but Ahn had a legal dispute with the club after refusing it. After FIFA intervened, Ahn was required to pay Perugia a compensation fee, which he did with the help of a Japanese entertainment company. This incident led to Ahn spending the next three years playing in the
J1 League instead of big leagues in Europe. He continued to maintain his form in the 2003 season, becoming the club's top scorer with 11 goals in 28 league appearances.
Yokohama F. Marinos In 2004, Ahn transferred to
Yokohama F. Marinos, the reigning J1 League champions. He quickly established himself as a key player, leading Yokohama to win the first stage. Although his performance was not continued in the second half of the season due to a mid-season injury, he became the team's top scorer with 12 goals in 25 league appearances. Yokohama secured back-to-back league titles by defeating second stage champions
Urawa Red Diamonds in the championship play-offs after his contribution. In 2005, Ahn continuously showed his impressive form, scoring four goals in nine appearances before receiving an offer from
Ligue 1 club
Metz.
Metz In July 2005, Ahn signed a one-year contract with Metz in the Ligue 1. Another J1 League club
Nagoya Grampus offered about four times more salary than Metz, but he chose to return to Europe. However, he underperformed at Metz, scoring only 2 goals in 16 league matches. Metz struggled throughout the season, eventually facing relegation even after Ahn left the club in winter.
MSV Duisburg In January 2006,
Blackburn Rovers invited Ahn to a tryout for them, but Ahn refused their offer in order to request a definite deal. In February, he secured a 17-month deal with
Bundesliga club
MSV Duisburg. He aimed to acclimate to the environment of Germany, the host country of the
2006 FIFA World Cup, ahead of the tournament. He scored two goals in 12 outings, and Duisburg was relegated to the
2. Bundesliga. He was interested in a move to
Heart of Midlothian of the
Scottish Premier League after the end of the season, but it fell through. Released by Duisburg in August, he returned to South Korea.
Suwon Samsung Bluewings In January 2007, Ahn joined K League club
Suwon Samsung Bluewings on a one-year deal. He initially showed promise, scoring a hat-trick in a
League Cup match against
Daejeon Citizen. However, his performance declined, and he was left out of the national team for the
2007 AFC Asian Cup. While playing for the reserve team in a
R League match to regain his ability, Ahn tried to get into the stand after being verbally abused by
FC Seoul fans. He was consecutively ejected from the match and had to pay a fine. Ahn's stint at Suwon was ultimately underwhelming, scoring 5 goals without a league goal in 25 appearances. He left the club at the end of the season.
Return to Busan In 2008, Ahn returned to his former club, now known as
Busan IPark. His performance at Busan was statistically not outstanding, but set an example for his teammates. Busan offered him a contract extension including the best treatment in the team after the season, but he looked forward to playing in one of foreign leagues, especially the
Major League Soccer.
Dalian Shide thumb|200px|Ahn with Dalian Shide</a> in 2009 On 20 March 2009, Ahn joined
Chinese Super League side
Dalian Shide on a seven-month contract until the end of the 2009 season. Quickly attracted to Ahn's performance, Dalian executives extended his contract for another year in less than three months. Despite his old age, he played a key role in Dalian's attack, becoming the team's top scorer in 2009 and 2010. Especially, Dalian reached fourth place in the league standing with three matches left of the
2010 season, approaching an
AFC Champions League berth under his influence. However, a knee injury sidelined him for the last matches, and his team finished sixth after failing to earn any victories during his absence. Ahn re-signed with Dalian for the 2011 season, but his prime was finished that year. On 29 October 2011, he wore the captain's armband in his last match at Dalian, and bade farewell to Dalian fans at half-time of the match. He announced his retirement as a player in January 2012. == International career ==