The imponderables of football, it's what makes it great.
Costello being injured is a blow no doubt but it alllows space for somebody else, an unknown or lesser known, to get a chance. Or possibly for an old guard to make the most of it.
Think a large factor, possibly the defining factor, this year will be how the squad are managed fitness-wise. The more tailored approach taken this year might leave lads under-prepared, or it might gear them up nicely. If it's the former we're in trouble but if it's the latter we could really kick on.
(Connolly being out until any potential semifinal could be seen as being a welcome addition to the approach taken, his return will add an extra dynamic to what is a clearly planned for period.)