Scott Quinnell is troulbled by the same knee that he hurt last summer in Australia and will miss Saturday's match against Scotland at the Millennium Stadium.
"It is the same knee, but it is a new injury," said Quinnell. "I just need a few weeks rest before the Heineken Cup semi-final for Llanelli against Leicester."
However, there was good news for Wales as Llanelli fly half Stephen Jones came through his club's Principality Cup quarter-final and also Cardiff centre Jamie Robinson was back in action in another quarter-final.
Both Robinson and his brother Nicky, along with Mark Taylor (Swansea) and Ian Gough (Newport) were in training with Wales over the weekend and Nathan Budgett (Bridgend) is hoping to be fit after limping off against LLanelli at half-time last Saturday.
Quinnell was the only one of the 22 players of the squad beaten by England at Twickenham who did not train.
The winners of a filmmaking competition organised by the education charity Into Film and the WRU enjoyed a behind the scenes tour of the Millennium Stadium - and a chance to be photographed with the WRU's fire-breathing, rugby loving mascot, Scorch The Dragon, and Welsh international, Jake Ball.
The Wales Under 20 camp are in a quietly confident mood as they face Ireland in the U20 Championship, with Coaching Co-Ordinator Allan Lewis and full back Dafydd Howells targeting a top five finish in the tournament.
Wales U20 may start as favourites against Japan this evening in the U20 Championship, but Team Manager Mark Taylor is warning against complacency. He is also hoping a good win will boost morale and 'kickstart' performances.
Coach Richard Hodges is hoping Wales U20 can put a disappointing campaign behind them when they tackle Japan tomorrow as they look to finish the U20 Championship strongly to secure a good seeding for next year's tournament.