The 26-year-old was forced off after falling badly on his right shoulder just four minutes into Ulster's impressive 19-8 victory over Glasgow. He will undergo tests today to determine the extent of the injury which centres around the AC joint.
Early estimations suggest that Boss is looking at a lay-off of between two and four weeks, and if it is a month he will certainly miss Ireland's championship opener against Wales on February 4 (Millennium Stadium, kick-off 3pm).
The New Zealand-born player, who took his Test caps haul to five during the Guinness Autumn Test Series, is also likely to miss Ulster's upcoming Heineken Cup games against Llanelli and Toulouse.
Saturday's win saw Ulster continue to lead the way at the top of the Magners League, with tries from Rory Best, Neil Best and Tommy Bowe seeing Mark McCall's men to victory.
With Leinster pressing for top spot and his first choice half-backs David Humphreys and Boss on the injury list, McCall will be banking on Paddy Wallace and Kieran Campbell to step up to the plate, and the former Irish international has no concerns on that front.
Game-time for Wallace at out-half will be key if he is to nail down a place in the Ireland 22 for the trip to Cardiff.
Speaking after the win in Glasgow, McCall said: "I thought Kieran had a smashing match, replacing Isaac early on, and Kieran and Paddy combined brilliantly at half-back.
"Kieran has been starved of opportunities and Paddy has been waiting for his chance (at number 10) and he has built on what has been a really good season for him. He had a top match and was devastating at times and was instrumental in two of our tries.
"The platform, however, was laid for him by what happened up front. Our scrum was really solid and our lineout was good and we got at theirs," he added.
"That is what you have to do away from home. You have got to be able to soak up pressure and we did that."
Only a bonus point win will do for Ulster against Llanelli next Saturday as they try to cling to an outside chance of making the Heineken Cup quarter-finals. Kick-off at Ravenhill is at 1.35pm.