In conditions sent to test the most seasoned professional, St Michael's and Castleknock delivered a hugely intense, highly committed first-round encounter at rain-sodden, wind-beaten Donnybrook.
At the end, the holders deservedly emerged unscathed, but not before Castleknock, inspired by dynamic flanker Jack O'Neill and all-action scrum-half Daragh Henry, had asked the most searching questions.
To their credit, the reigning champions had all the answers, with the final scoreline – two converted tries to a James McCormack penalty – fairly reflecting the overall balance of play.
Ross Molony and his troops will be happy to have made it through but, much like Terenure on Sunday, they know they will need to improve again, irrespective of who is next up in the quarter-final.
On the most vile of days, both teams went at it hammer and tongs. Unsurprisingly, mistakes proliferated as the wind and rain proved a mighty leveller.
Castleknock showed little respect for their much-vaunted opponents in the early exchanges and they took the lead just four minutes in when full-back McCormack landed a penalty from the left of the posts.
Leinster schools marksman supreme Ross Byrne had the chance to equalise in the 10th minute, but the wind drew his penalty attempt wide.
Undaunted, and with outstanding hooker Richie Allen to the fore, the St Michael's eight continued to turn the screw deep inside Castleknock territory.
Just 12 minutes later they got their reward when prop Denis Coulson crossed to translate territorial dominance into points. Byrne added the extras and the Michael's challenge was up and running.
Byrne had another penalty opportunity to stretch the lead, but again the wind proved too strong. Indeed, it's not too often you witness both teams in the same match opting for the scrum as the preferred option instead of kicking.
That said, Michael's did have a couple of gilt-edged opportunities when first full-back Cian Kelleher and then Allen (along with lock James Ryan the most impressive players on the day) put boot to ball when a simple pass would have yielded better dividend.
In the second period, Kelleher and Ryan began to exert a much greater influence in broken play. They both made huge yardage through hard, direct running at key times in the contest as Castleknock, despite losing O'Neill to injury, continued to trade tackle for tackle.
Their efforts deserved better, but the only try of the second half went to out-half Byrne, who crashed over under the posts. The same player then added the extras to give his side a 14-3 lead.
With Daragh Scanlon and Niall O'Riordan in the vanguard, Castleknock battled right to the very end, but the holders never relented.
The message is clear: on this early evidence, and despite the horrendous conditions, it's going to take a very good side to beat them.
St Michael's – C Kelleher; D Green, A Leavy, M Gilsenen (M O'Keefe 73), O O'Meara; R Byrne, N McCarthy (J O'Connell 68); H Redmond (N Quane 63), R Allen (C Duffy 63), D Coulson; R Molony (capt), J Ryan; C Cregan, A Penny, J Murphy.
Castleknock – J McCormack; M McQuillan (D Byrne 55), S McEntaggart, K Dixon, C Doddy; K Doyle (S Quinlan 59), D Henry; M Bennett, T Hanlon (K Murphy 70), Z Butt; E Murphy, J O'Sullivan (C Lacey 37); D Scanlon, J O'Neill (Captain) (A McNally 45), N O'Riordan.
REF – D Keane (Leinster Branch).