In the same period, Leko also lost to Ernesto Hoost, Jorgen Kruth, Jerome LeBanner, Francisco Filho, and Mark Hunt.
After a six-fight win streak in 2003 (5-0 in K-1) that included wins over multiple time K-1 champion Peter Aerts, heavyweight kickboxing champion Mike Bernardo, and K-1 World Grand Prix finalist Francisco Filho, the now top-ranked Leko was a favourite leading into the K-1 World Grand Prix 2003.
However, the striker was unable to find his place there, losing three successive fights to grapplers, and in 2005 he returned to the Muay Thai and kickboxing worlds.
He made his return to top level kickboxing with Golden Glory for Dutch major league promotion It's Showtime, in 2005.
A rematch was booked in K-1, and Hari returned the favour, winning via spectacular spinning back kick, the move noted for being Leko's trademark.
Leko's last major success to date came when he won his second K-1 World Grand Prix in Las Vegas tournament, beating Scott Lighty, Carter Williams and then Michael McDonald in the final.
Golden Glory claimed the stoppage was too quick, but nevertheless, Leko was out of another World Grand Prix - his last appearance in the final 16.
Dropped out of almost every top 10 heavyweight rankings, Leko began to compete almost exclusively in the Netherlands and Germany, with varying results.
On the back of two consecutive losses in K-1, Leko went into the fight as an underdog, but he ended up dominating Manhoef for two rounds, picking him apart with boxing and leg kicks.
After beating Volkan Duzgun on Fightingstars presents: It's Showtime 2010, Leko entered the Ultimate Glory heavyweight tournament, where he drew Wendell Roche in the quarter-finals.
[citation needed] The retirement talk was officially put aside as Golden Glory confirmed that Leko would be returning to face old foe Jerome LeBanner on June 11, 2011, in Geneva.
He was even said to be intent on securing a rubber match with old foe Badr Hari, if he could string together some wins to get ranked and merit a final grudge encounter with the Moroccan.
He competed in a four-man tournament at GFC Series 1 in Dubai, United Arab Emirates on May 29, 2014 and had his rubber match with Badr Hari in the semi-finals.
[2][3] Leko suffered a twenty-one second high kick knockout loss at the hands of Zabit Samedov on the undercard of the Ruslan Chagaev vs. Fres Oquendo boxing match in Grozny, Russia on July 6, 2014.
[citation needed] On May 30, 2003, Leko failed a drug test prior to K-1 World Grand Prix 2003 in Basel.