Leinster scrum coach Robin McBryde believes last week's defensive display against Glasgow Warriors was "unacceptable".
Leinster out-scored the Scots by five-tries to three to run out 40-21 winners at the the RDS, and six-points clear at the top of the Guinness PRO14's Conference A.
They make the trip to Kingspan Stadium on Saturday for a game with Ulster that could go a long way to deciding who makes the Grand Final.
McBryde described the game as being "all to play for".
However, some screws need to be tightened in defence on the evidence of last week's win over Glasgow.
"Just our tackling in general really, we fell off quite a few tackles," the former Wales coach said.
"The number of missed tackles was completely unacceptable. The players knew straight after the game in the changing room.
"Scott Fardy spoke up and said... personal pride is what you carry with you. A level of intensity... and there's no better sign with regards to that in how you go around in defending, and how much pride you take in your one-on-one tackles.
"We just fell off quite a few. It was very uncharacteristic of us. So nobody was happy.
"We were left grabbing, as opposed to getting a good shoulder contact against the opposition.
"So that's one thing that we've got to put right, because you look at the threats that Ulster pose - especially in the backs - powerful runners, great footwork."
Harry Byrne is a doubt for the game with Ulster, as he undergoes the return-to-play protocols.
Josh van der Flier, Rhys Ruddock, Ross Byrne and Ed Byrne all parachute in from the international squad.
One of the 23 players staying in Ireland camp is Jonathan Sexton. The Leinster and Ireland skipper put pen-to-paper on a new one-year central contract on Tuesday.
"It's great, long may he continue really," McBryde said of the extension.
"There's a few really experienced players really putting their hand up - Alun Wyn Jones to name but one - and Johnny's no different.
"[He's a] quality player, and a big player not only for us in Leinster, but for Ireland as well. So that's great news."
When asked if he was surprised by the shortness of the Sexton deal, McBryde replied, "You take every year as it comes when you get to a certain age. The body will tell you if you can go on.
"And if the body won't, the mind certainly will.
"Somebody like Johnny, they expect high standards. And if you start falling short of those standards then you know yourself that it's time to move on.
"He'll make that decision when it's right and proper.
"So long as he's enjoying his rugby... and in the current climate there's not a lot else going on, so we're very fortunate to play rugby and that's going to keep him going as well."