Most likely performance would be affected. Sub frequencies around 80hz and below are omnidirectional, they travel out in all directions and you can't detect that direction, just feel it. Think what happens when you throw a pebble into a pond, the ripples travel away in all directions around that location. That is what happens with low bass frequencies. So basically, I think some of your performance would be sacrificed by doing this.
Also, there is no guarantee the front wall is the best place for your sub in your room even if you don't enclose it in the wall. Did you try the "sub crawl" to determine this location, or just pick it by convenience?
Often when using one sub, placing it near a corner that is furthest from other openings into other rooms, may give you the best outcome. Multiple subs centered on opposite walls is more ideal, but often out of peoples budgets.
