Tom Shanklin and Sam Warburton will boost the Blues backline and back row respectively as they host Newcastle Falcons on Sunday (1500).
"There are a couple of players who have made recent returns from injury and are in need of game time so for them it has been an easy decision to make," said Wales head coach Warren Gatland.
"It doesn't get any bigger than a visit to Twickenham to start off a Six Nations campaign and we must make sure we get our preparation exactly right.
"That means some players remain in camp for the fortnight and there are others who will benefit from seeing some senior rugby action this weekend."
English premiership prop duo Eifion Lewis-Roberts and Rhys Gill will also return to club rugby this Friday night, Gill's Saracens head to Leeds Carnegie and Sale Sharks host Northampton Saints.
LV= Cup Round Three Fixtures:
Friday, January 29
19:30, Newport Gwent Dragons v Ospreys (S4C)
19:30, Leeds Carnegie v Saracens
19:45, Sale Sharks v Northampton Saints
Saturday, January 30
15:00, Gloucester Rugby v Worcester Warriors
17:45, London Wasps v Scarlets (Sky)
Sunday, January 31,
15:00, Cardiff Blues v Newcastle Falcons
15:00, London Irish v Harlequins