At the start of the 2015–16 NHL season Vainonen and Nashville agreed to mutually terminate his contract, allowing him to seek employment elsewhere.
[2] He returned to his native Finland, coming to terms with Ässät Pori of the top tier Liiga.
[3] On June 19, 2019, Vainonen opted to continue in the EBEL agreeing to a one-year contract with the Dornbirn Bulldogs.
[4] In a COVID-19 affected 2020–21 season, Vainonen played for Orli Znojmo, HC Frýdek-Místek and Italian side SG Cortina.
In August 2021, Vainonen agreed terms with Scottish EIHL side Glasgow Clan for the 2021–22 season.