Ireland coach Joe Schmidt is "quietly confident" tight-head prop Mike Ross will be fit for the first Test against South Africa in Dublin on 8 November.
Front-rowers Marty Moore and Nathan White have been ruled out by injury, while Ross, 34, has not played for a month because of a groin problem.
However, Schmidt said Ross is "progressing pretty well" and expects him to resume training next week.
"He's taken part in some of the more static aspects of training," he said.
Ireland begin their three-Test November series against South Africa without at least 15 squad members missing because of injury.
James Cronin will miss the series with ankle trouble, compounding Ireland's loose-head prop problems and adding to Jack McGrath's workload with Cian Healy a long-term absentee.
Schmidt said he considered pulling tight-head prop options Rodney Ah You and Archer out of club action this weekend.
"Rodney Ah You is playing for Connacht against the Ospreys, and Stephen Archer will have some time at Munster," Schmidt said.
"Tadhg Furlong will play for Leinster and Declan Fitzpatrick for Ulster - those are our other options.
"It's a catch-22, because Nathan White was the starting prop at Connacht and has really dominated the starting time [and] Rodney needs the game time.
"Tadhg Furlong certainly needs to play; he's been sat behind Michael Bent.
"Declan Fitzpatrick has been massively underplayed because he's had a succession of injuries and Stephen Archer the same.
"So it's not a lot of rugby for those guys in the last two weeks to then have a week off and go into a Test match, it would be pretty difficult."
Tommy Bowe and Gordon D'Arcy joined Ireland's list of injury concerns following last weekend's European action.
Bowe suffered concussion in Ulster's defeat by Toulon on Saturday, while D'Arcy hobbled off during Leinster's win over Castres with a groin injury.
Rob Kearney is also a doubt for Ireland's South Africa contest because of a hamstring injury.
Andrew Trimble, Luke Marshall, Iain Henderson and Donnacha Ryan will miss Ireland's three autumn Tests, while Leinster trio Fergus McFadden, Dave Kearney and Jordi Murphy are also out of action because of injury.
|Ireland's injury count|
|Cian Healy (hamstring) out of autumn series|
|James Cronin (ankle) out of autumn series|
|Nathan White (arm) ruled out for four months|
|Marty Moore (shoulder) out until New Year|
|Donnacha Ryan (toe) out until New Year after surgery|
|Iain Henderson (hip) ruled out until New Year|
|Andrew Trimble (toe) out for several months|
|Luke Marshall (knee) misses November games because of knee injury|
|Rob Kearney (hamstring) doubtful for South Africa game|
|Gordon D'Arcy (groin) doubtful for Springboks game|
|Tommy Bowe (concussion) doubtful for South Africa game|
|Mike Ross (groin) out of action for past month|
|Fergus McFadden (ankle) out of action for past month but nearing fitness|
|Dave Kearney (knee) yet to play this season because of a knee injury|
|Jordi Murphy (elbow) out since September but close to return|