In the 2014–15 season, after not being drafted by an NBA team, Fieler started his career with
Club Ourense Baloncesto in the Spanish
LEB Oro. He won the Playoffs with Ourense, which earned the club the right to promotion to the first-tier
Liga ACB. For the 2015–16 season, he signed with
Donar Groningen in the Netherlands. After winning the championship in 2016, he re-signed with Donar for another season. On November 15, 2016, Fieler set a new
FIBA Europe Cup record with an
efficiency of 46 in a 98–70 victory against
Limburg United. In the 2016–17 season, Fieler was named to the
All-DBL Team and was awarded the
DBL Statistical Player of the Year Award. Fieler won his second Dutch title with Donar that season and was named the
DBL Play-offs MVP after averaging 13.7 points in the play-offs. He won the Belgian championship two consecutive years with Oostende, while also playing in the
Basketball Champions League. On June 24, 2019, Fieler signed a deal with
Promitheas Patras of the
Greek Basket League. He averaged 8.5 points and 2.3 rebounds per game and was selected to play in the
HEBA Greek All Star Game. On July 28, 2020, Fieler signed with
Brose Bamberg of the German
Basketball Bundesliga. He averaged 9.4 points and 3.2 rebounds in the
2020–21 season. In July 2021, Fieler signed in Japan with
Utsunomiya Brex. He won the 2021–22 B.League championship with Brex. On June 28, 2022, Fieler signed with fellow Japanese club
Saga Ballooners. On June 20, 2023, Fieler re-signed with Saga Ballooners. On May 21, 2024, Fieler re-signed with Saga Ballooners. In December 2024, he has been diagnosed with a rupture of the anterior cruciate ligament in his left knee. ==Honors and titles==