Dellien started playing tennis at the age of five. He was able to achieve his first successes on the junior tour. His biggest success in a Junior Grand Slam was at the US Open in 2011 . In singles he made it to the second round, in doubles to the quarterfinals. His best placement was a combined 2nd place in the junior world rankings .
On the professional tour, Dellien mainly plays tournaments on the lower-class ITF Future Tour and ATP Challenger Tour . So far he has won 16 singles and 17 doubles titles on the Future Tour. In 2009, Dellien played his first tournaments on the professional tour. Until October 2012 he only played on the Future Tour. At his first challenger tournament in Montevideo , he received a wildcard for the double field, but lost the opening match with Santiago Maresca . In Cali he was again in a main draw of a challenger. In doubles he made it into the second round, but was eliminated in two sets. In August 2013 he was in the top 400 in both singles and doubles. In 2014 he was in his first Challenger double-final with Eduardo Schwank , which they lost in two sets. On the Future Tour he won various tournaments in doubles and made a jump in the world rankings, so that at the end of the year he was in the top 200 in the world. In the following year Dellien could not build on the performances, which is why he slipped in the world rankings in singles and doubles to 500th place. This tendency continued, he only recovered in mid-2017 and won several future tournaments in individual, so that at the end of the year he was again in the top 200.
He had a breakthrough in 2018 . He won three tournaments in two months. In Sarasota he prevailed against Facundo Bagnis in three sets in the final , in Savannah he defeated Christian Harrison and in Vicenza he won against Matteo Donati . As a result, in June he was in 113th place, his best placement to date. With his triumph he achieved the first tournament victory of a Bolivian since Mario Martínez almost 35 years ago.
Dellien has played for the Bolivian Davis Cup team since 2010 . His balance in singles is 20: 7, in doubles 6: 3.
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Bolivia
Sarasota
Facundo Bagnis
Vicenza
Santiago de Chile
Wu Tung-lin
Danilo Petrovic
Campinas
