Jones has been thrown into the boiler house for the Ospreys' Heineken Cup showdown with London Irish at the Liberty Stadium on Friday night.
The European clash with the Aviva Premiership leaders is Jones' first start of the season after he suffered deep bruising on his country's summer tour to New Zealand.
The 29-year-old has only recently returned to full training, with fellow Welsh international Jonathan Thomas impressing in the back row in his absence.
"Jonathan Thomas was asked to fill the void at No8 because of Ryan's injury and he has done exceptionally well. I promised him at the start of the season that once a bloke gets the shirt, it's up to the others to get it off him, and we are supporting his form as a coaching team," said Ospreys boss Scott Johnson.
"Saying that, we've certainly missed Ryan's contributions. We wanted him in the team.
"To put Ryan at eight and move JT to lock changes everything - calls, line-outs - and we didn't want to go down that path for a five-day turn-around.
"The team needs Ryan's effectiveness and his work-rate, but it's too complicated to start moving everyone around. We are very happy with JT, and Ryan is happy to do this for the team.
"We feel Ryan has had enough game time now to warrant his place at the start. If we had two weeks then, maybe, we would do it differently."
Although Johnson has suggested Jones will still feature in the back row later this season, he has also made it clear that the switch to No4 or 5 could well become a permanent one next term.
Jones still hopes to captain Wales from No8 at the 2011 World Cup but Johnson would be far from surprised if we see plenty more of him at lock after the global gathering.
"Ryan has played there before and I genuinely believe that after the World Cup we'll probably see a bit more of him there," added Johnson.
"He's such a brave and industrious player and, the way the game is going, he will give us a competitive edge."