A grim night for the visitors to the RDS. And it could have been much worse.
Andy Friends' men trailed Leinster 26-0 by the close of the first quarter in this Guinness PRO14 encounter. That the injury-hit westerners managed to concede just north of the same total again from there to the finish was something of a relief.
A record defeat looked to be a given for Connacht when they trailed 40-0 at the interval. As it is, a 58-0 loss to Cardiff back in 2008 and a 58-point loss to Saracens in Europe six seasons ago remain the two worst blots on their copybook in the professional era.
Leinster were sensational at times with tries from Max Deegan (2), Dave Kearney, Ciaran Frawley, Joe Tomane, Luke McGrath, Garry Ringrose (2). Tom McCartney finally got Connacht off the mark inside the last ten minutes with a converted try.
Did it? Did any of it? Leinster had the four-try bonus point secured after 20 minutes, having claimed the first five-pointer inside two minutes. An injury-ravaged Connacht, also deprived of the rested Bundee Aki and Jack Carty, were simply blown away.
That is 14 games unbeaten now for Leinster who have yet to feel the sting of defeat this season. Their last competitive loss was the Heineken Champions Cup final to Saracens last spring and they are carrying a light casualty list. Frightening.
This could have been Leinster's biggest ever win in the Celtic League, in all its various forms. It wasn't to be. Their 70-6 slaughter of Zebre this month three years ago remains their high point in terms of destructiveness.
This is deeply worrying for Connacht whose previous effort was a 35-3 defeat in Belfast. Their hopes of making the knockout stages in Europe were already slim after the third round loss in Gloucester but their prospects look especially grim now as Toulouse loom large on the horizon.
Leinster were just better, faster and stronger in the collisions. Name the department and they dominated. That they came up off the accelerator as time went on was only natural for a side aiming to be top seed when the European pool stages are over later this month.
Leinster were without 16 internationals here for a variety of reasons – plus James Lowe – but they still fielded nine men who have played test rugby. Rhys Ruddock got the official nod but there were impressive individual efforts all round.
James Ryan came off after just 24 minutes with a knock to the leg and we'll have to wait and see just what the injury is and how serious it could prove to be. Not a man you want to see struggle with the Six Nations around the corner.
Leinster, already qualified for the knockout stages, entertain Lyon at the RDS in round five of the Heineken Champions Cup next Sunday. Connacht play host to Toulouse in Galway the afternoon before in a game they simply must win.
J Larmour; F McFadden, G Ringrose, J Tomane, D Kearney; C Frawley, L McGrath; P Dooley, S Cronin, T Furlong; R Molony, J Ryan; R Ruddock, W Connors, M Deegan.
R Baird for Ryan (24); C Doris for Connors (HT); B Byrne for Cronin, E Byrne for Dooley and C Kelleher for Kearney (all 51); J Gibson-Park for McGrath (60); H Byrne for Frawley (60); R Salanoa for Furlong (64).
S Fitzgerald; N Adeolokun, K Godwin, T Daly, J Porch; C Fitzgerald, C Blade; D Buckley, S Delahunt, D Robertson-McCoy; N Murray. G Thornbury; E Masterson, P Boyle, R Copeland.
T O'Halloran for S Fitzgerald (24); T McCartney for Delahunt and P McAllister for Buckley (both 45); D Horwitz for Porch (51); J Maksymiw for Thornbury (54); S Kerins for Blade (60); S Masterson for E Masterson (60); C Kenny for Robertson-McCoy (61).
N Paterson (Scotland).