Scarlets flanker Turnbull will win his fifth cap in Wales' Autumn Test series opener against Argentina at the Millennium Stadium, packing down alongside back-row colleagues Sam Warburton and Toby Faletau.
It represents a huge opportunity for the 24-year-old at the start of a campaign when Wales will also face Samoa, New Zealand and Australia.
But it is a group of games they must tackle without injured blindside specialist Dan Lydiate, who was player of the tournament in last season's Six Nations Championship.
With former Wales captain Ryan Jones also absent this weekend, Turnbull has received the call from interim head coach Rob Howley. "Dan's boots are big ones to fill," Turnbull said. "He is a credit to himself with what he has achieved in the past 18 months, especially the Six Nations player of the season award, and you can see how much he puts into it.
"I am looking forward to it on Saturday. Sam and I grew up playing age grade rugby together. He took his opportunities and has gone on from there."