Answer
Before managing Celje, Riera managed Olimpija Ljubljana. He was appointed manager of Olimpija in May 2018, replacing Darko Milanič. He led the club to third place in the 2018–19 season, and to the 2019 Slovenian Cup Final, which they lost to Maribor. He was sacked by Olimpija in October 2019, with the club in seventh place in the league.