The New York pair were in action on opposite coasts and fell to the second and first defeats of their professional careers respectively.
A meeting between the two, who fought as amateurs with Smith [23(19)-2(1)] coming out on top, has been long mooted, however they both lost in separate world title eliminators.
35 year old Monaghan [28(17)-1(1)] was blitzed out inside two rounds by the hugely impressive southpaw Marcus Browne [20(15)-0] at the Nassau Coliseum in his native Long Island on a Premier Boxing Champions card.
‘Irish Seanie,’ of Navan descent, took the defeat in good grace, and noted afterwards that “I’ve whooped a lotta ass in my life and tonight I got mine whooped! I want to sincerely thank everyone who came out and supported me! I love you all and you’ve given me a gift I will never forget!”
“Also, big props to my man Marcus Browne, future champ and the best guy I’ve ever been in the ring with. The world is yours bro, go take it.”
Watch the Marcus Browne v Seanie Monaghan stoppage below:
Across the country at the Inglewood Forum in California on a HBO Boxing After Dark card, Smith fell to a unanimous decision defeat.
The Irish Bomber took on Cuban Sullivan Barrera [20(14)-1(0)], who has only ever been beaten by Andre Ward, and was outpointed over ten rounds – after the fight was mysteriously downgraded from a twelve rounder at the last minute.
Smith began well, downing Barrera with a left hook to the crown in the opening round, however the Caribbean boxer would take control as the fight wore on and claimed a 97-92 x2, 96-93 win on the cards.
It would emerge afterwards that Smith had his jaw broken in the opening round, but still fought through until the bell.
Watch highlights of Joe Smith Jr v Sullivan Barrera below:
Both will now look to rebuild, and Smith especially may need time, however it is hoped that the two Long Islanders may eventually meet in the ring for a fight that has been years in the making.