Up and coming Wests Tigers rugby league player Mosese Fotuaika has been found dead, aged 20.

A NSW police spokesperson said officers were called to a townhouse in the south western Sydney suburb of Merrylands at about 6.50pm AEDT on Thursday.

They confirmed a 20-year-old man was dead inside the premises.

The death is not being treated as suspicious.

Fotuaika looked set to make his senior debut after playing in several trial matches.

He was a member of the Tigers' 2012 premiership-winning under-20s team.

The Wests Tigers official Facebook site posted notice of the loss while players such as Tim Moltzen and Aaron Woods shared their condolences on Twitter.