Jānis Bērziņš who in childhood was raised in Latvian most northern town Rūjiena started his professional career in 2009 with BK Valmiera.

First he played major role for Valmiera, that won Latvian League bronze medals, which was followed by invitation to participate in Adidas Eurocamp, which was held in Treviso, Italy.

In August 2013, after an impressive showing with Latvian team in U20 European Championship, Bērziņš signed an extension with VEF Rīga.

In 25 league games, he averaged 5.7 points, 3.4 rebounds and 1 assist, playing around 18 minutes per contest.

In July 2013, Bērziņš was big part of Latvia's historic run at U20 European Championship in Tallinn, Estonia, which was highlighted by making finals, while Jānis was named to All-Tournament team.