Jonathan Sexton limped out of Ireland's frustrating four-try, 32-15 defeat to Australia, suffering a hamstring injury scare.
The distraught Racing Metro fly-half buried his face in his hands as he left the Aviva Stadium field at half-time.
Despite crossing the line twice, Joe Schmidt's Ireland were unable to conjure a try and will be furious with the defensive lapses that led to Hooper's first score, and Cooper's soft finish.
Cooper opened the scoring with a ninth-minute penalty, before Sexton levelled from the tee after a strong Ireland rolling maul.
Queensland Reds fly-half Cooper then fluffed a straightforward penalty, but the Wallabies struck quickly.
Australia's most-capped hooker Stephen Moore revealed in the week how he could have ended up representing Ireland.
The 87-cap front-rower rejected Irish Rugby Football Union advances as a 19-year-old, stemming from his Irish parents.
Not even a stint living in Ireland as a toddler before moving to Australia could convince him to consider representing his parents' homeland.
How Schmidt and Ireland would have happily had him in green when he bisected their midfield, before producing a scoring pass even Brian O'Driscoll himself would have savoured.
Cummins received Moore's pass, cut in off his left wing and outfoxed the remaining cover to notch his third Wallabies try.
New head coach Joe Schmidt spent all week telling his players just how foolish it would be to kick away cheap ball to the Wallabies.
So he would have been spitting feathers when Tommy Bowe cleared loosely from his own 22 and straight into gleeful Australian clutches.
Cooper's whipped pass sent Folau to the line, Australia worked the ball back left and Fardy's back-handed offload ripped Ireland apart.
Openside Hooper was left with a clear run home for his first international score.
Ireland rallied immediately, Fitzgerald's flat mis-pass sending McFadden into the Australia 22.
Peter O'Mahony knocked on after sustained phase play, but then Ireland won a free kick at the scrum.
Heaslip's number-eight break brought two tight sneaks towards the line, before Reddan failed to deliver the killer pass.
After all the pressure, Sexton had to settle for a penalty.
McFadden's searing break yielded another penalty that Sexton knocked over with Hooper sent to the sin-bin.
Another fluent Irish attack brought Sexton's fourth penalty of the night, closing an engaging half missing only a home try.
Leinster's Ian Madigan replaced Sexton at half-time, with the Racing Metro fly-half suffering that potential hamstring problem.
Another flat Cooper pass sent Cummins into the left corner from Australia's bright start, but Bowe did just enough to deny him his second try.
English Television Match Official Geoff Warren reviewed the play, and rightly ruled a knock-on.
Australia turned Ireland over at the scrum though, and Cooper struck all too easily from the set-piece.
The wily outside-half claimed his seventh Australia try, ghosting between Madigan and Luke Marshall's wafer-thin resistance.
Cooper landed his second penalty after Rob Kearney's uncharacteristic high-ball spill.
Ireland's scrum power then brought a penalty, that Madigan duly converted.
Ireland punted a kickable penalty to the corner to launch the final quarter, only to knock on at the line-out when Australia sacked their maul at source.
The Wallabies took that cue to wrestle back control and quickly scored through a line-out drive of their own.
Flanker Hooper rose from the pile of bodies with the ball, to confirm his second try of the night.
Tevita Kuridrani was then sent off for a dangerous tackle on flanker O'Mahony.
The Australia centre flipped the Munster back-rower and planted him on his head, and can have no complaints with the decision ruled by TMO Warren.
Replacement Conor Murray thought he had scored from a penalty snipe, but referee Chris Pollock brought back the play, refusing to allow the quick tap.
O'Driscoll, Marshall and Jack McGrath dragged Ireland close again, and Sean Cronin powered over.
The replacement hooker was denied his first Ireland try though, with the TMO chalking it off due to a Murray knock-on in the build-up.
Two games in the honeymoon period is well and truly over on the Schmidt era, while Ireland produced several promising sections, the visitors more than merited victory.