It was Warren Gatland's sworn intent to take his Grand Slam-winning team on tour to South Africa in June, but his plans may still be hamstrung by injury late in the season.
With Mike Phillips ruled out of the tour because of knee ligament damage, Dwayne Peel could also join the rested/recovering list after leaving the Scarlets' Magners League win over the Blues last week with a recurrence of the shoulder injury that forced him out of the Six Nations opener against England.
It leaves Gatland short in the position, with Gareth Cooper stuck largely on the bench at Gloucester and and only the untried Matt and Ryan Powell of Worcester, and Warren Fury of London Irish, as back-up.
"I am very concerned," admitted Gatland to the Western Mail.
"Dwayne took a bit of a knock at the weekend and we have got Gareth, but he is not starting regularly for Gloucester.
"Perhaps the loss of Mike would have given us a chance to get some form back into Dwayne or develop another number nine."
Jones is to undergo a scan on Wednesday on a niggling groin problem, with Scarlets boss Phil Davies stressing the need for careful management.
"We've spoken to the union and we'll all know more by the end of week, but the injury's been niggling Mark both during the Six Nations and after," said Scarlets director of rugby Phil Davies.
"It's been managed, but if a player's getting a niggle in a particular area, you've got to explore it.
"It might just be treatment and rest that's needed, but we'll have to see what the scan shows up.
"Whatever happens, it's a long-term appreciation of the player's welfare that's the key thing.
"There's a lot of rugby over the next three or four years for these players and we've got to keep them as fit and as healthy as possible."