In a performance that was a world away from the title contenders they have looked in the early weeks of the A-League season the Wanderers turned in a lethargic and disjointed performance that harkened back to the Wanderers woes of the first half of last season.
A 25 yard missile from Adelaide's Daniel Adlung was the difference between the two sides as the Reds booked a final showdown with Sydney FC on November 21st, it's United's second Cup final appearance after they claimed the inaugural competition in 2014.
It was a defensive error that gift wrapped the visitors the lead in the 12th minute when Jonathan Aspro failed to clear from the back, his miscue found Adelaide midfielder Johan Absolonson who calmly slotted the ball past Vedran Janjetovic.
The Wanderers were also lucky to not be a man down when Roly Bonevacia put his studs through Adelaide's Isaias yet was only given a yellow card, for his part Isaias got his revenge with a hard foul on Bonevacia moments later which put him in the book.
Jonathon Aspro was also lucky to stay on the pitch after earning a yellow card during a period where he conceded three fouls in a minute, likewise Jacob Melling who went in hard into a challenge on Jordan Elsey with the Adelaide defender left bruised in the aftermath yet only a foul was given.
The Wanderers had 13 shots to 8 yet only two were on target, one chance that went wide was in the 58th minute when Jack Clisby launched a ball into the six yard box yet Riera's goalscoring nous eluded him as he headed it wide from point blank range.
The Wanderers were gifted a lifeline in the 70th minute when Brendan Santalab converted a penalty after being fouled in the box by Isaias, but it was all to no avail as the Wanderers lacked the killer blow required and their FFA Cup derby final against Sydney FC went out the window.
This Sunday the Wanderers meet the Newcastle Jets in a W-League/A-League double header, catch both matches live and free on SWR Sport with the W-League live streamed on SWR Sport from 2:15pm and the A-League on SWR Sport and SWR Triple 9 (99.9FM) from 4:30pm.