Cardiff Blues prop Jenkins is set to be out for up to five weeks after suffering a knee injury in his region's Heineken Cup victory over Racing Metro.
That makes Jenkins the third first-choice player to be ruled out of Wales' opening Six Nations clash with Ireland at the Aviva Stadium a week on Sunday, with locks Alun Wyn Jones and Luke Charteris left out of coach Warren Gatland's squad due to long-term injuries.
Gatland also has injury doubts over fly-half Rhys Priestland (knee), centre Jamie Roberts (knee) and flanker Dan Lydiate (ankle).
Gatland admitted at this week's Six Nations launch that the loss of 83-cap forward Jenkins, who is also likely to miss the home game against Scotland, is a huge blow to his side.
But the Blues prop was badly troubled by niggling toe and calf problems during 2010 and 2011, with James stepping into the loosehead jersey to good effect on those occasions.
And Jones, 30, has every confidence that his Ospreys team-mate will once again prove to be a more than able deputy.
He said: "Paul has always done very well when he has been called upon.
"He is a different type of prop to Gethin in that he is a bit more set-piece orientated, while Gethin is like having an extra back-row forward on the field.
"So what we lose in one area we can gain in another. They are both good all-round players and I have no doubt that Paul will make sure we are not weakened in that area."
While Jenkins is the only member of Gatland's initial 35-man selection to be ruled out of the trip to Dublin, fly-half Priestland, whose assured performances made him one of the stars of Wales' march to the World Cup semi-finals, is struggling to be fit for selection.
That has led to veteran fly-half Stephen Jones being called into their training camp in Gdansk, Poland.
Jones, who has won a record 104 caps for his country, was left out of Gatland's original party, but with Priestland's fitness proving a concern and James Hook having to return to Perpignan for their Top 14 fixture this weekend, the Scarlets playmaker will provide training cover.
Hook is likely to be handed the starting role should Priestland fail to prove his fitness for the Aviva Stadium clash, which would potentially leave Jones in line for a spot among the replacements.
Gavin Henson is the other outside-half option in Gatland's squad, but he has not featured at number 10 in his three appearances to date for the Cardiff Blues.
Wales' Dublin assignment will be a repeat of the World Cup quarter-final in Wellington, which they won 22-10.
But Wales have a poor recent record in Dublin, having won on just one of their last five visits to the city, and face an Ireland side thirsting for revenge after their premature World Cup exit.
And with the Irish provinces having been in excellent Heineken Cup form in recent weeks, Jones is well aware of the huge task facing the visitors.
"It is going to be pretty tough, they are very good in Dublin," said the 75-cap tighthead. "They showed that with the way they gave England a mauling last year.
"We know they will be coming in with an element of revenge, we have seen what (Ireland captain) Paul O'Connell has had to say, but we are confident going into this game.
"Their provinces have done very well - although if you look at Ulster a lot of their key players are South African - but the guys who play for Leinster and Munster, they know how to win big games and they will be on a high.
"We are confident after what we did at the World Cup, although we have to remember that we also lost three games out there; we got to the semi-finals but we did not achieve what we set out to do.
"We know in Dublin that we will have to turn up and be at the top of our game."
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