An interception try from Harri Millard sealed Cardiff a 20-17 victory over the Lions to cement their place in the top six of the URC table.
The enduring class of Taulupe Faletau, Liam Williams and Josh Adams on their returns gives Wales hope after a wretched year.
Gareth Davies will captain Wales against the Reds after Cory Hill's late withdrawal moments before kick-off for personal reasons.
Grace scored 89 tries for St Helens in his league career.
Warren Gatland has confirmed his 34-player Wales squad that will leave for Australia on June 26 ahead of a two-Test series against the Wallabies.
The ball-playing Ospreys loosehead is finding his voice as a leader he prepares to take on the fearsome Springboks pack
Cardiff back row James Botham has been drafted into Warren Gatland's Wales squad ahead of their encounter with world champions South Africa at Twickenham on Saturday.
Cardiff slumped to an eighth successive United Rugby Championship defeat after being dispatched 34-13 by the Lions in Johannesburg.
Wales player ratings: A fourth defeat and a one-sided scoreline might point to a team that struggled to match France. And that is mostly true.