McGrath relishing his battle with 'mature' Hartley
The sight of Leinster coming to Franklin's Gardens on Friday night will evoke many painful memories for Northampton supporters and so too for Jim Mallinder who branded his side's performance in the 2013 defeat as "embarrassing".
Leinster were ruthless in their 40-7 mauling of the Saints but a week later at the Aviva Stadium, their concentration wavered and, as a result, they were beaten.
Franklin's Gardens has traditionally been a tough place for teams to travel to in Europe but the manner in which Leinster exposed their frailties ripped up that script.
Northampton may be struggling domestically this time around, but in Jack McGrath's eyes, they are a more dangerous outfit than three years ago.
But yet, Louis Picamoles hasn't quite had the desired impact since his big-money move from Toulouse in the summer, while the same can be said for JJ Hanrahan, who, on far less money than the French No 8, hasn't set the Premiership alight.
For all of the Saints' struggles this season, they pose serious threats all around the pitch and on their day can be devastatingly powerful.
"It's a really intimidating place and it was tough to go over there," McGrath, who started at loosehead in the convincing win in 2013, insists.
"It's a new competition for them, they can forget about how they're going in the Premiership, they're one win away from topping the group.
"It's going to be pretty tough and they have internationals coming back who are unbeaten and that's going to bring another positive and renewed energy into their team.
"We got the better of them over there and then I just remember when we came back to the Aviva it was 60 minutes of scrum and maul and we were just soaking up pressure. Fair play to them, they were good at that and I don't think much has changed.
"There is a lot of experience and danger around the park. It's maybe something they didn't have the last time we played them. If anything they will be stronger."
Whether Northampton are in fact stronger remains to be seen, but their ninth-place position in the Premiership would not suggest so. Mallinder's side are likely to look to take the game to Leinster up front but given the amount of Irish internationals that Leo Cullen is set to recall, they know what to expect.
Northampton's controversial skipper Dylan Hartley will typify their physical approach as everyone else continues to watch to see if he has fully turned that seemingly elusive corner. Eddie Jones thinks so and since he made the hooker captain, England are unbeaten.
McGrath could well find himself in the same Lions front-row as Hartley next June and he fully respects how he has turned his career around.
"I haven't played against him a whole lot but to watch him play he doesn't take a step backwards," McGrath observes.
"He leads from the front and guys follow and that's the type of guy you want on your team. I have a lot of respect for him. He has come back from whatever troubles he had and completely forgot about it. Like a lot of players he has matured and he has been given that opportunity now to be English captain and I don't think he has put a foot out of place since.
"Some people are a bit mad when they are younger and he seems to have grown out of it. Again, I don't know the guy. He's shown that he can eradicate that from his game. It's been really good for him because he has had a successful time since that.
"You can only give a guy respect for that and he is a quality player as well. He's a leader of men, people will follow him. It will be a good battle because his bread and butter is scrum and lineout and breakdown. It'll be good to go against a calibre of player like that."