trying to outmuscle the English scrum with 4 people and 1 injured scrummaging is never going to work.
Why can't o'brien, ferris and heaslip push with the rest ?
heaslip spends his entire time in the scrum looking up - he can't scrummage like that. the other two are just watching for breakaways and don't put the full push on either.
The front row of a scrum consists of:
The hooker, whose job it is to hook the ball back on the put-in.
He is flanked by his two props: one is the tight head prop whose head is inside the scrum and the other is the loose head prop whose head is outside the scrum.
If you look at a scrum you will appreciate that each side has two props; it is impossible to have anything other than tighthead and loosehead props.