Champions Cliftonville endured something of an inevitable reaction after their triumphant weekend as they were well beaten by Glentoran.
The Reds had only four starters from Saturday's memorable title-clinching win over Linfield.
Andy Waterworth followed his superb ninth-minute opener with another fine goal three minutes later at the Oval.
Substitute Carl McComb added the third Glentoran goal on 77 minutes moments after coming on.
Glentoran's players formed a guard of honour to congratulate the new champions before the start.
However, Tommy Breslin's decision to field only Ciaran Caldwell, Eamonn Seydak, Jaimie McGovern and Stephen Garrett from Saturday's starting line-up against the Blues, meant that the Oval contest scarcely measured up as an Irish Cup Final dress-rehearsal.
Garrett did have a good early chance for the Reds but was denied by Elliott Morris who also had to block a Martin Donnelly effort moments later.
But Waterworth opened the scoring at the other end in the ninth minute as he outpaced Dermot McVeigh before firing a terrific effort to the roof of the net past Ryan Brown.
Within three minutes, Waterworth had doubled Glentoran's advantage as he cut inside from the left before delivering another great shot past the Reds keeper.
Garrett tried hard to rally the under-strength champions with some strong running while Seydak also went close to replying before half-time.
However, Glentoran were looking the sharper outfit with David Howland's impressive work in midfield complementing Waterworth's enterprise.
With the departure of Caldwell and Garrett further depleting the Reds, the game became a dull affair in the second period.
McComb was only on the pitch for 30 seconds when he ran on to a long ball over the top before planting the third goal past Brown on 77 minutes.
The result meant only Cliftonville's fourth defeat of the season but one suspects that Tommy Breslin won't have been unduly perturbed.