Valley endured a torrid Boxing Day at Butlin Road as Mickleover ran out easy winners.
After lively start from Rugby, the hosts allowed Mickleover to get a strong foothold in the game and they made it pay with two goals in ten minutes before half time - adding a third mid-way through the second half to end Town's run of six straight Boxing Day (or equivalent) victories.
Teddy Rowe replaced long-term knee injury victim Isaac Adegoke in the only change to the previous starting line-up, although there were returns to the match-day squad on the bench for Trey Charles, Callum Griffin and Stan Anaebonam - who had re-signed for the club on Christmas Eve following a short spell at NPL Premier side Ashton United.
Valley made a great start to the game, and dominated the opening ten minutes or so with a number of forays exclusively down their left flank. Tyrell Hamilton, Geoff Lundoloki and Rivel Mardenborough all put in dangerous crosses that were just about dealt with in the opening few exchanges, with Hamilton also having a shot blocked after he had cut in from the same wing.
For Miclkleover, Andy Dales's in-swinging free-kick drifted just beyond the upright, before Town were back at the visitors again, with Mardenborough's low shot to the near post capably turned behind for a corner by keeper Jack McDowell after Caine Elliott's teasing pass over the top of the defence had created another opportunity down the left hand side.
McDowell again did well by fingertipping Will Harris's header to Rowe's set-piece delivery over the bar, before Mickleover finally threatened at the other end when Marcus Bald was off his line to spread himself to deny Dales at close quarters.
Meanwhile, Mardenborough almost capitalised on a through ball, with McDowell just managing to scramble to the ball away before the danger was ultimately cleared.
The remainder of the period belonged to Mickleover though, and Will Atkinson's shot was saved by a decent stop from Bald's legs, whilst George Wilkinson's on-target strike from a central position also cannoned back off a Town body.
The opening goal came on 34 minutes, after Atkinson had fed Thabang Dube on the edge of the box, and the tricky winger somehow managed to shake off the attentions of two Town defenders before neatly steering the ball past Bald and into the bottom corner.
Bald then executed a relatively comfortable take to a Dales near-post free-kick, before the away side probably should have made it two when Dales's searching cross from the right reached Paddy Webb well-placed in front of the goal, but fortunately for Town the ex-Quorn man's touch let him down and Bald was able to gather the ball.
However, Valley's respite was short-lived, and Dube made it two-nil just before half-time with a powerful strike after a great move that had seen Webb, Atkinson and Dube himself - with an exquisite flick - open up the Town defence.
Rugby emerged brightly for the new period though, and Josh Thomas was soon heading one over the bar, before McDowell pulled off a top drawer save to keep out Elliott's goal-bound effort - with Hamilton somehow unable to scramble in the rebound from a couple of yards out.
Dales flashed a good opportunity wide as the visitors looked to make the game safe, and Brad Gascoigne then almost capitalised on a Bald handling error, with Webb's speculative effort from distance also bouncing wide of the frame.
Bald did do well to claim a low cross from Dube and also to scoop the ball as Dales threatened to finish off a run in behind the Town defence, but he could do little to prevent Mickleover's third which came after Rugby switched off momentarily to allow Louis Bonser to get a strike in which looped up off Thomas and into the net on 66 minutes.
Rugby did search for a consolation in the closing twenty minutes, with Elliott's shot blocked and Charles's acrobatic attempt missing the target - both from Anaebonam's assists.
Town's afternoon was probably summed up though when captain Sam Tye lifted one over from a great position after Lundoloki had done well out on the left, and then Callum Griffin dragged a weak shot wide - with Anaebonam again the provider.
Bald saved Josiah Dyer's low shot late-on, with Bald also preventing Dales capping a fine individual performance with a goal of his own in stoppage-time.
