McGrath’s punishment wasn’t confined to a yellow card, or even the penalty try awarded to Castres. Isa Nacewa put the tin hat on it by stepping in to firefight at nine and stealing a poacher’s try off the base of a ruck while he was at it.
“I knew someone was going to mention that,” McGrath laughed. “Isa comes in and scores a try; typical him really. He’s obviously a world-class player. Johnny said it to me while I was in the sin bin: ‘You might as well stay there’.
“He taught me a lesson.”
The lesson in question was to remember what you are good at.
Recognised as a talented, sniping nine long before he emerged onto the senior scene four years ago, McGrath doesn’t disagree when it’s suggested that he has maybe moved away from that.
That suspicion was framed at the RDS last weekend when the St Michael’s graduate broke away into open prairie at one point before choosing to lay off to Joey Carbery when more profit was available in backing himself.
“Yeah, it was tough to watch that on the video review. Nine times out of 10 I score that. It’s easier to say now but at the time I gave it to Joey. If I had given it to him a second earlier it probably would have given him a hand.
“I just need to look up and run over the line really.
“It’s probably something I need to go back to or keep working on. There was a try or two there for me.”
Truth be told, it wasn’t a great day for him.
The quality of his passing wasn’t at the standard required at times. Nacewa’s was appreciably more consistent, so was that of Jamison Gibson-Park when he was ushered in for the final few laps.
McGrath is four seasons and 55 caps into his Leinster career and this is his big opportunity now that Eoin Reddan and Isaac Boss have put away their boots. At 23, he has the chance to open up a long and fruitful career.
This Sunday in Montpellier offers another shot at self-improvement.
Like nine of his colleagues in last weekend’s squad of 23, McGrath has never played a European game in France though he won a FIRA U18 European Cup with Ireland in Tarbes five years ago.
McGrath was skipper of a side that saw off France in the semi-final and England in the decider and one that also contained such talents as Stuart Olding, Dan Leavy and Robbie Henshaw.
Fast forward five years and McGrath and Henshaw were half of a potentially explosive 9-10-12-13 axis that also included Joey Carbery and Garry Ringrose and one with an average age of 22.
“We were just chatting about this,” said McGrath. “I’m the oldest of the four lads and they’ve been giving me a good bit of slagging over it. The lads at 10, 12, 13 are all naturally good footballers.
“They all play their own game and we have been focusing on their strengths. We haven’t thought about combinations or anything. Everyone has been playing their own game and they seem to feed off each other very well.”
More will be required of them this weekend.
And the odd McGrath snipe would be nice too.