The Premier League icon, 45, is in charge of Shelbourne in his homeland, where he is becoming known for his antics.
After yesterday’s win over St Patricks, Duff went straight to the stands to grab a fan.
The delighted fan delivered an X-rated team talk, which the players clearly loved.
Duff was not in such a good mood after a 0-0 draw with Shamrock Rovers on Monday.
The former Chelsea winger slammed his own player in an astonishing rant after the fan-favourite was sent off.
He blasted: “I used to laugh about his diet, in year one, the chicken fillet rolls, whatever.
“That time has passed now. How you live your life off the pitch, how you train usually gets shown up on a match night and it did.
“I get he’s a fan’s favourite and what have you, but he hasn’t deserved to play.
“Not one bit. Flashes. I could go on and give you a flash. I’m 45 and I can’t walk.”
Duff also delivered an incredible interview about being in trouble with his wife.
After a dip in form, he said: “Sometimes a bit of tough love, harsh words earlier on in the week.
“Later on in the week I probably wasn’t even speaking to them – they weren’t speaking to me.
“It’s probably what my wife does to me when I’m in trouble and she gets a better husband at the end of it.”
And Duff also made headlines with his reaction to keeper Scott van der Sluis joining Love Island.
He said: “I was shocked and saddened that Scott chose a villa in Mallorca full of beautiful, single women over myself, the staff and the players.
“I thank Scott for his services to Shelbourne FC and we all wish him the very best for the future, whatever that holds.”
Tactics Exposed: Why Kai Havertz is Arsenal’s most important player
By Dean Scoggins
KAI HAVERTZ endured a difficult start to life at the Emirates after his big-money move from Chelsea.
But has now well and truly found his feet.
The German, 24, has found his scoring boots in recent weeks, including his double against his old club.
But Havertz has been providing much more than goals in recent months.
In fact he has become Mikel Arteta’s most important player as Arsenal go for the title.
That’s after the Spanish boss made a genius tactical switch.
Click here to read all about it.
Or to watch the brilliant video in full on YouTube.
Shelbourne are three points clear in the League of Ireland Premier Division and travel to Dundalk next Friday.
All eyes will be on their manager to see what he gets up to next.