The 22-year-old Cardiff Blues centre led Wales to a 54-9 victory over Uruguay in Pool A, only to pick up a hamstring injury that put a premature end to his participation in the tournament.
Hallam Amos is another youngster who impressed on Sunday, the Newport Gwent Dragons winger carrying for 108 metres and adding a try of his own.
Ospreys flanker Justin Tipuric crossed once and Scarlets scrum-half Gareth Davies twice, while the latter's GUINNESS PRO12 teammate Samson Lee also got on the score sheet - though a calf complaint has put his fitness in question too.
Ireland also kicked off their World Cup with a half-century of points against Canada and Jonathan Sexton was at the heart of almost everything in Cardiff.
The fly-half, who will return to Leinster after the tournament, made eight tackles at a completion rate of 100 per cent, grabbed a try and added nine points from the tee in the 50-7 triumph.
There were also scores for his provincial teammates Sean O'Brien, Sean Cronin, Rob Kearney and Dave Kearney - the latter with his first international try since his 2013 debut.
Ulster duo Iain Henderson and Jared Payne also crossed the whitewash, while Scarlets new boy - and GUINNESS PRO12 champion - DTH van der Merwe grabbed Canada's only try.
Elsewhere there was frustration for Glasgow Warriors' Fijian lock Leone Nakarawa and Edinburgh's Tongan winger Will Helu, who suffered defeat to England and Georgia respectively.
Leinster full-back Zane Kirchner played 80 minutes for South Africa but couldn't prevent Japan completing an historic victory in Brighton on Saturday.
And - later that day at Twickenham - an Italy team packed with Zebre and Benetton Treviso players slipped to a 32-10 defeat at the hands of France.
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