Stephen Ferris believes Ireland are carrying too many injuries and some of the players are simply not match-fit.
Jordi Murphy, Joey Carbery, Rob Kearney, Robbie Henshaw, Chris Farrell and Johnny Sexton have had or are nursing injuries, while Jack Conan returned home after suffering a fractured foot in training.
The squad have seven days before the next outing, a match against Samoa that can pave the way for a quarter-final tilt.
But former Ireland back row Ferris reckons that more players need to get more field time and is worried that time is running out.
"You can run all day and do as much strength and conditioning work as you want pre-season but when it comes down to it it's about getting match-minutes," the Ulster man told the RTE Rugby podcast.
"Johnny Sexton played 63 minutes in four warm-up games, he came off against Scotland, he didn’t play against Japan, he came off at half-time against Russia.
"Are some of our 31-man squad fit? I don’t think they are.
"Why is Robbie Henshaw out there? We haven’t seen a minute of him.
"Joey Carbery misses out again. I think having negativity around people who aren’t generally fit actually breeds into the squad and people will start to doubt themselves."
Ferris also revealed his frustration at watching Ireland struggle against Russia, who only qualified for the tournament following the disqualification of Belgium, Spain and Romania.
He added: "I couldn't believe what I was watching in some parts of the game. I watched it again and I found myself hitting the fast-forward button a lot and that was due to the amount of errors, mistakes, scrums, reset scrums.
"The ball-in-play time wasn’t high.
"As an Irish fan and after watching the game twice it’s left me feeling very frustrated and wondering are Ireland good enough to get beyond a quarter-final? They are running out of time to come good.
"I think it’s more of a mental thing than anything. There were a few concerning things for me.
"Tadhg Furlong, arguably the best tighthead prop in the world, comes on and gets destroyed in the scrum, the scrum looked like it was all over the place.
"Iain Henderson, one of the best tighthead locks in the world comes on, the scrum was going backwards."
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Follow Ireland v Samoa on Saturday 12 October (kick-off 11.45am) via the live blog on RTÉ.ie/Sport and the News Now App, watch live on RTÉ2 or listen to live match commentary on RTÉ Radio 1.
