His place in the starting line-up on Saturday is taken by Ospreys colleague Alun-Wyn Jones, with Gloucester's Will James joining the replacements.
Evans has not played since suffering a serious shoulder problem last December, so there can be little doubt Wales coach Gareth Jenkins is taking a gamble.
Wales team physiotherapist Mark Davies said: "We anticipate Ian returning to fitness as we head out to Nantes for the World Cup.
"The results of our investigations this morning were the best we could have hoped for, revealing a simple ligament strain to the joint where his collarbone meets his sternum.
"It is a stable injury and will now require rest and treatment with a view to him returning to full training in up to three weeks' time."
Jenkins added: "We selected Ian on merit against Argentina, so this is a setback for him, but now Alun-Wyn Jones will come into the second-row with Will James also on hand to provide cover from the bench.
"Ian's opportunity now will depend on his recovery, but the good news is that he is going to be available to play rugby in the World Cup, and that his injury should settle down in time."
Evans joins Llanelli Scarlets fly-half Stephen Jones in being unable to play before the World Cup.
Jones suffered a groin-related injury during Wales' World Cup training camp in Brittany last month, but is expected to be fit for the tournament opener against Canada on September 9.