Encouraged by last week's 17-10 win at Banbridge, Rainey came into this game with plenty of confidence. That confidence could also be felt pre-match amongst the large crowd at Hatrick Park.
But the visitors, who flew up from east Cork, had other ideas and although they trailed 7-3 after 33 minutes' play, Midleton were soon ahead.
Rainey suffered a sin-binning before half-time and conceded two tries while down to 14 men.
Current Munster backs coach Jason Holland, who lined out at out-half, had a hand in the first Midleton try as he put up a lovely cross-field kick for winger Paul Whelan to gather and score from.
Holland turned provider again when he put a pinpoint kick for full-back Jeff Hitchmough to touch down.
Michael Glancy, Rainey's full-back and try scorer in the first half, missed a penalty chance to reply early in the second half.
But Midleton soon found another gear as centre Junior Sifa, a recent recruit from New Zealand, passed for Hitchmough to grab his second try.
It was more of the same on 54 minutes when man-of-the-match Sifa charged through for a try which put the visitors 29-10 ahead.
As Rainey began to slip off their tackles, Midleton took full advantage to turn it into a rout.
Michael Cronin, Damian Smyth, Sifa and Whelan all added tries, allowing place-kicker Hitchmough to take his tally for the afternoon to 27 points (2 tries, 1 penalty and 7 conversions).
Portadown's trip south to Musgrave Park on Saturday was a profitable one as they came away with a bonus point 22-11 win over Sundays Well.
The Ports started brightly and got a stranglehold on possession with Kiwi full-back Tom Overy standing out as strong kicker and clever distributor.
Overy darted forward to make the half-break which led to the visitors' opening try from Jon Holden, which went unconverted.
The Well hit back with a penalty from Chris Burnett, making the half-time score 5-3, and the Cork side's out-half followed up with another three-pointer during the opening stages of the second period.
Team captain Declan Coppinger and his forward colleagues Mick Moynihan and Til Selting stood out as Sunday's Well wrestled back control at the control, rucking and mauling with great intent.
But Hika Reid's Portadown side were just too good in the end. The visitors cantered clear thanks to tries from Stuart Douglas, man-of-the-match Overy and hard-working flanker Diarmuid O'Kane.
David Twohig grabbed a consolation score for the Well, who missed out on a further bonus point-clinching try.
At Parsonstown, Barnhall prop Colm Dufficy crossed the whitewash but the Blue Bulls were overpowered by Connemara in a 26-5 defeat.
The Galway side had young half-back Sean Joyce to thank for their first win of the league run. Joyce brilliantly kicked seven penalty goals to add to Paddy O'Toole's try.
County Carlow maintained their recent winning form with a battling 14-3 victory at Nenagh Ormond.
David Delaney kicked a penalty for the Tipperary outfit, but a try from Richie Whyte and a hat-trick of penalties from Cian Moore nudged Carlow home.
Naas broke their duck in this season's league with a 28-19 triumph away to Waterpark. Trailing by six points at the break, the Kildare men roared back and Joey Moran scored a decisive late try.
Waterpark hit the front through out-half Ricardo Santos. A recent recruit from South Africa, he linked with Gerry Miller before scurrying over from close range for a sixth-minute converted try.
Santos continued to influence the game and he picked off a superb drop goal from 35 metres for a 10-0 Waterpark lead.
Naas out-half David Aherne replied shortly afterwards with a penalty. The scores dried up before Santos kicked his first penalty and then Naas grabbed an excellent try.
They counter-attacked after a smashing tackle by Ted Walsh on Adolf Sweigers had released the ball. Moran kicked on and Henry Bryce scampered ahead and scooped up the ball for winger Johnny Delaney to dot down under the posts.
Aherne converted but Santos swung over an injury-time penalty to leave Waterpark 16-10 ahead at half-time.
Outside centre Bryce helped Naas take the lead shortly after the restart. After a series of rucks, Aherne, Aiden Tyrell, Andrew Kearney and Delaney all got their hands on the ball before the latter put Bryce through for his score.
Aherne's conversion edged Naas ahead and a 58th-minute penalty from the number 10 made it 20-16.
Santos managed to claw it back to a one-point game, as he landed another penalty for a 19-point personal tally.
Yet Waterpark could not compete with the powerful Naas forwards in the scrum and the hosts were twice driven back in the set piece before Naas scored another penalty.
Good work from Tyrell, Moran and lock Jeremy Hikuroa set up the place-kick for Aherne who took it with aplomb.
And the result was put beyond doubt in injury-time when Hikuroa galloped forward and up to the 22 before he offloaded for Moran to cross the whitewash.
Meanwhile, at Donnybrook on Saturday, Old Wesley handed Banbridge a 34-17 beating thanks to tries from Brian Hastings (2), Philip Hosie, Barry McLaughlin and Alan Thompson.
Wesley actually led by 34-0, early in the second half, after some exemplary play. Skilful scrum half Dan Van Zyl was to the fore and spun the ball wide at almost every opportunity.
Bann struggled to cope but they did regain control of possession and territory for a large part of the second half, working Claude Crawford, Pieter Odendaal and Alan Gibson over for tries.
Palepoi Nonu, a powerfully-built centre, crashed over for the deciding try in Suttonians' 23-19 victory over Queen's University at the JJ McDowell Memorial Grounds.
Nonu scored in the last play of the game. Queen's play-maker Ian Porter kicked four penalties and converted Jonny Shiel's second try of the season but it was not enough in the end.
Ards missed out on their first win of the league campaign as they missed three kickable penalties and conceded an intercept try in a 21-13 loss to Corinthians.
The Galway visitors had tries from Wayne Williams and Michael Roche, as well as an 11-point kicking contribution from fit-again Connacht player Tim Donnelly.
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