Indeed, anything that could have gone wrong for the Candystripes did go wrong, the home side losing the services of skipper Ryan McBride due to a late tackle in the 28th minute when 2-0 in arrears.
A third Dundalk goal, five minutes before the interval, ended this fixture as a contest, Derry limping off at the break having been taken apart by the reigning champions.
Now six points clear of Cork with a rearranged home fixture against Longford Town on Tuesday night at Oriel Park before their Champions’ League, Stephen Kenny will have few complaints.
The Lilywhites couldn’t have asked for a better start when breaking the deadlock within the space of two minutes.
Having won a corner from their opening attack, the lively Daryl Horgan floated the ball towards the back post. Brian Gartland headed the ball downwards and when Derry keeper Ger Doherty appeared to make a block, Dave McMillan showcased his predatory instincts when squeezing the ball home from close quarters.
Delighted with their bright opening in the sunshine, the visitors continued to press and when Stephen O’Donnell sent Horgan scampering clear in the 9th minute Doherty did well to get down to parry the shot wide at the expense of a corner.
Not to be outdone, the home side threatened in the 15th minute, Niclas Vemmelund delivering a teasing cross into the Dundalk penalty area before Rory Patterson met the ball on the full, his effort touched over the crossbar by the alert Gary Rogers.
However, always looking assured in possession, Dundalk punished Derry’s defensive frailties for a second time in the 20th minute.
Awarded a free-kick on the right, former Derry midfielder Patrick McEleney curled the ball into the danger area and the totally unmarked Dean Massey gleefully flicked it home with his first touch and the home lot were in serious difficulties.
Indeed, that worry was compounded eight minutes later when home skipper Ryan McBride was shown a straight red card by referee Paul McLaughlin in an incident which silenced the Brandywell crowd.
The centre-back lunged into a late tackle on Stephen O’Donnell as he raced forward in a threatening counter- attack and the Monaghan official had no option but to send the defender off for an early shower.
Two goals to the good and now facing 10 men, the champions retained possession so well, and were always patient.
While Doherty earned his wages with another superb save to deny McMillan a second goal, there was nothing the Derry goalkeeper could do when McMillan was rewarded with his second and his side’s third goal in the 40th minute.
Full-back Brian Gannon found the striker in acres of space on the right flank and, having moved forward, the Dubliner stroked the ball home as the unprotected Doherty advanced.
Derry ended the opening period with a superb run by Barry McNamee and, while surrounded by three defenders, the midfielder forced Rogers into a magnificent save.
The 10 men did show some heart following the change of ends but it was Dundalk who struck a fourth goal in the 59th minute. McMillan was again denied by Doherty but as the loose ball spun up into the air, Horgan smashed it high into the net from close range.
And McMillan had the final say when celebrating a hat-trick and Dundalk’s fifth of the night.
Doherty; Vemmelund, McBride, Barry, Jarvis (McClean, 70); McCormack, McEneff; Schubert (McDermott, 38), Monaghan (Boyle, h/t), McNamee; Patterson.
Rogers; Gannon, Gartland (Barrett, 78), Boyle, Massey (Grimes, 65); Finn; Horgan (Meenan, 68), O’Donnell, McEleney, Mountney; McMillan.
P McLaughlin (Monaghan).