The Cork fighter was stopped in the opening round of his WBA middleweight world title final eliminator at the T-Mobile Arena by David Lemieux.
Now 34 years of age with his record standing at 28(20)-3(2), the Mahon man has options in front of him and decisions to make.
Below Irish-Boxing.com looks at what could be next for Spike
Taking in a disclosed purse of $400,000 and with plans to buy a house for himself and his family in Togher, no one could complain if O’Sullivan decided to call it a day.
However, this is one route we can rule out, with O’Sullivan promising that he will be back as he continues his chase for big fights and big titles.
The Lemieux fight was the second of a potential four fight ‘options’ deal with Golden Boy Promotions and, encouragingly, the U.S. giant have stated their intention to retain the services of the Celtic Warriors man despite the loss.
A move down in weight has been mooted for years and O’Sullivan confirmed in the aftermath that it is his intention to drop down six pounds to the 154lbs light middleweight class.
On Saturday the Leesider rehydrated up to 164lbs – far below the eye-watering 179lbs reached by Lemieux. O’Sullivan, whose training has intensified massively since last year, believes he is well able to healthily move down to the lower weight and it is a move that could hugely benefit him.
Golden Boy’s Jaime Munguia holds the WBO title at light middleweight although a move north for the giant Mexican looks likely in the near future as they seek to marinate a fight with Canelo.
Away from Munguia, Jarrett Hurd holds the WBA and IBF belts while another American, Jermell Charlo, holds the WBC strap.
One potential fight at light middleweight which piques our interest is an all-Irish brawl with Brisbane-based Kildare fighter Dennis Hogan. Ranked #1, but not mandatory, by the WBO, the Kilcullen man is currently considering his next move and his team have a good working relationship with Golden Boy
Indeed there are a number of fighters in the Golden Boy stable the would look to fit the bill for O’Sullivan including Japanese warrior Yoshihiro Kamegai and Brazilian Patrick Teixeira.
Golden Boy’s chief matchmaker Robert Diaz stated in the aftermath that he would like to match O’Sullivan with Quigley – although, as a first world title defence for the Donegal middleweight.
While he was close to taking on Japanese star Ryota Murata, Quigley looks a good few fights away from fighting for a world title – indeed, a fight with O’Sullivan would look to be perfect as something of an eliminator.
While ‘letting fights build’ can pay off in a big way, more often than not it can lead to mooted match-ups never taking place – and one only needs to look at Ireland’s last crop of top middleweights: Andy Lee, Matthew Macklin, an John Duddy.
On that note, there are big all-Irish fights aside from Jason Quigley. Dennis Hogan has already been mentioned while O’Sullivan is not overly fond of Coalisland’s Conrad Cummings. This match-up would be a war – while a clash with friend and former stablemate Luke Keeler would certainly intrigue.
The long-mooted move down to light middleweight does look the likeliest next step for Spike – especially if it is Golden Boy’s intention to put a clash with Jason Quigley on the long finger.
The Rebel offered no excuses following the Lemieux defeat, noting that he had put in the hardest camp of his life. While the ending was violent, the instant nature of it meant that O’Sullivan left Las Vegas without suffering major physical damage and he intends to return to training this weekend.
Eager to push past the defeat, O’Sullivan is keen to fight again soon, and a date before the end of the year looks entirely feasible.