[3] In August 2014, he made his debut for Kapfenberg's second team in the fourth-tier Landesliga Steiermark, when he was in the starting eleven on the first matchday of the 2014–15 season against SV Anger.

In May 2015, he was included in the first-team squad of Kapfenberg for the first time for a match against SC Austria Lustenau, but he did not make an appearance.

In August 2015, he was in the starting lineup for the first time for the first team in the match against SKN St. Pölten, being before replaced by Gerald Nutz at halftime.

In May 2017, Flecker joined Austrian Bundesliga club Wolfsberger AC, where he signed a two-year contract.

On 2 July 2018, despite an ongoing contract with WAC, he moved to recently promoted TSV Hartberg on a free transfer.