From BR Bullpen
- Bats Right, Throws Right
 Biographical Information
Jansen debuted in Hoofdklasse in 2002 with RCH. He was 3-5 with a 4.40 ERA and ranked among the league leaders in ERA (8th), innings pitched (59 1/3, tied for 5th) and strikeouts (45, fifth). In 2003, Jansen moved to the Tornado's. He finished sixth in ERA (2.78), 7th in innings (90 2/3), tied for 5th in complete games (2) and 6th in strikeouts (64).
Jansen joined the Dutch national team for the 2003 Baseball World Cup, but was awful in a 12-2 loss to Japan. He relieved in the 7th and allowed hits to two of five batters he faced. He hit another and one reached on error. He only retired one. He finished with a 54.00 ERA and 81.00 RA as he made no more appearances in that tournament.
In 2004, Jansen switched clubs again, joining Kinheim. He finished 6th in ERA, now down to 2.05. His 105 1/3 innings tied Eelco Jansen for second behind Manny Olivera. Jansen also was 5th with 64 strikeouts that season.
Jansen was 4-6 with a 3.63 ERA in a disappointing decline in 2005. For the first time, he missed the top 10 in the league in ERA. He was slated to pitch for the Dutch entry in the European Championship but was injured and Gregory Gustina took his spot on the roster.
Jansen moved to the bullpen in 2006. He was 4-1 with 3 saves and a 2.31 ERA while allowing 32 hits in 46 2/3 IP. He tied for fifth in the league in saves. He was 1-0 with a 1.13 ERA in 3 appearances in the 2006 Holland Series.
Jansen was even sharper in 2007, with a 2-1 record, one save and 0.78 ERA. He only surrendered 18 hits in 34 2/3 IP and struck out 36 to help Kinheim post the best record in Hoofdklasse. He led the league in ERA and lowest opponent batting average (.157) while tying for fifth with 20 appearances. He rejoined the Dutch team for the World Port Tournament and a historic visit to the US. In the 2007 European Championship, he pitched two hitless innings, fanning four to help the Dutch claim the Gold Medal and a spot in the 2008 Olympics. He threw one scoreless inning for the champion Kinheim in the 2007 European Cup.
In the 2007 Holland Series, Jansen pitched 3 1/3 scoreless innings to help Kinheim take the title again.
Jansen threw 8 2/3 scoreless innings in the 2007 World Port Tournament, allowing 3 hits and going 1-0. Jansen was the worst Dutch pitcher in the 2007 Baseball World Cup, posting a 16.20 ERA and allowing five of ten opposing batters to reach base. The Netherlands still finished 4th overall.
Jansen went 1-1 with a 3.41 ERA and a save in 25 games for Kinheim in 2008. He led in appearances but tied for 8th with 35 walks (in only 34 1/3 IP!). He allowed 8 hits and 5 runs in 3 1/3 postseason innings.
In the 2008 European Cup in Grosseto, Jansen pitched two scoreless innings as Kinheim won the title. In the Matino phase of the 2009 European Cup, Duko allowed two hits and one unearned run in 5 1/3 IP in a win over the Templiers de Sénart. He tossed one shutout inning in the Final Four of the Cup.
Sources: Honkbalsite.com, Dutch statistics, Marco Stoovelaar's Dutch baseball site, Defunct IBAF website, Mister Baseball European baseball site, 2008 European Cup in Grosseto, 2009 European Cup in Matino, 2009 European Cup Final Four