- Bats Right, Throws Right
- Height 6' 4", Weight 195 lb.
Thieben made it to the Bundesliga-1 in 2010 with the Dohren Wild Farmers. He allowed six runs (two earned) and eight walks in 5 1/3 IP; at the plate, he was 5 for 23 with 4 walks. He fielded under .900, with his main position being second base. In 2011, he had a 2.01 ERA in the Bundesliga-2 for the Buchbinder Legionaere Regensburg. He participated in the MLB European Academy that year. In the 2011 European Junior Championship, he had a 1-1, 6.30 record and 6 walks in 10 innings. He got a win in relief against Russia. Starting against Italy in the Bronze Medal game, he allowed four runs in seven innings but took the loss. He then made the German squad for the 2011 Baseball World Cup, a surprise as he turned 18 shortly before the tournament began and hadn't pitched in Bundesliga-1 that year. He pitched two games in the World Cup, with wildly divergent results. Against the Dominican Republic, he was the top German hurler. Relieving Jens Cornelsen, he hit Alex Castillo but then retired Jose Campusano, Freddy Guzman, Chris de la Cruz and Willis Otanez. Max Schmitz relieved Thieben. In his other outing, he relieved André Hughes in the 7th with a surprisingly close 4-2 deficit against Cuba. He allowed singles to Alfredo Despaigne, Yulieski Gourriel and José Dariel Abreu before Dominik Hartinger relieved him; all three runners would score.
The Seattle Mariners signed him in 2011; the scouts were Wayne Norton and Bob Engle. He made his pro debut the next summer with the AZL Mariners on Opening Day, June 20 against the AZL Padres. The final pitcher in a 15-7 loss, he allowed one run and 3 hits in 2 innings. He was 3-1 with a 4.02 ERA and 1.82 WHIP in 15 games for the AZL Mariners that year. He got one start for Germany in the 2012 European Championship, going 3 1/3 IP before Markus Solbach relieved in a 8-3 win over France. He was charged with one run as an inherited runner scored after he left. He relieved Will Ohman late in a loss to Team Canada in the 2013 World Baseball Classic Qualifiers, walking Jimmy Van Ostrand (the lone batter he faced) before Adam Kudryk relieved.
Thieben was 1-0 with a 6.95 ERA in 18 games for the 2013 Pulaski Mariners, posting a 2.23 WHIP. In 2014, he improved to 2-1, 2.73 in another 18 contests for Pulaski. He finished his US career 6-2 with a save and a 4.41 ERA in 51 games. He had a 1.92 WHIP, walking 70 in 79 2/3 IP. In the 2014 European Championship, he pitched two games out of the bullpen (3 IP, 4 H, 1 BB, 2 R, 4 K).
Let go by the Mariners, he returned to Germany but only pitched one inning for the 2015 Paderborn Untouchables (1 H, 1 BB, 2 K). Despite that very limited work, he was back in a German uniform for the 2016 World Baseball Classic Qualifiers. He wound up one of only three players to put up an infinite ERA in the first three qualifiers - and the other two pitchers (Kieran Cree and Ohman) allowed one run while retiring none while Thieben allowed three runs. He replaced Sven Schüller in the 8th with a 9-2 deficit against the Czech national team, two on and no outs. He gave up a run-scoring double to Mike Cervenak, intentionally walked Jakub Sládek and issued a four-pitch walk to Jakub Malik before Daniel Hinz relieved and promptly served up a grand slam.
He was 1-1 with a 4.05 ERA for the 2016 Untouchables, walking 15 while whiffing 24 in 20 IP. He also saw action as a backup OF/1B, hitting .414/.471/.483 in 35 plate appearances.