Lewis Ferguson dashed Steven Gerrard's hopes of leading Rangers out at the Betfred Cup final as his late winner sealed a 1-0 triumph for Aberdeen at Hampden.
The Ibrox boss was hoping to mark his first six months in charge of the Light Blues by leading them out against Celtic on December 2.
But Dons youngster Ferguson - son of former Ibrox hero Derek and nephew of ex-skipper Barry - wrecked those plans as headed home the winner with 11 minutes left.
Aberdeen have had a frustrating start to the campaign but they held firm to book Derek McInnes' fourth cup final from five years as Pittodrie manager.
Earlier, Celtic's sizzling second-half superiority saw them book their place in the final with a 3-0 win over Hearts at BT Murrayfield.
After a fairly uneventful and goalless first 45 minutes, the Parkhead side took the lead in the 53rd minute when Gorgie midfielder Oliver Bozanic tripped Ryan Christie in the penalty area allowing fellow substitute Scott Sinclair to slam in the penalty.
In a unique cup semi-final at the home of Scottish rugby, James Forrest capitalised on a mistake by Gorgie keeper Zdenek Zlamal to fire in an easy second.
Christie scored a wonderful third to set up a final appearance at Hampden Park on December 2 against Aberdeen.