Maccarinelli needed just two rounds to end Ellis's challenge
Enzo Maccarinelli stopped Matthew Ellis in two rounds in his heavyweight bout at London's ExCeL Arena.
Swansea's Maccarinelli, 28, had hoped to be fighting for his old WBO cruiserweight title but had a string of opponents pull out on him.
Maccarinelli had Ellis down twice in the first round with some savage body punches and Dave Parris called the fight off halfway through the second.
Maccarinelli hopes to fight for the WBO cruiserweight belt early next year.
Promoter Frank Warren said Maccarinelli would probably fight original opponent Johnathon Banks, who pulled out of the bill after suffering an ankle injury, in February.
Francisco Alvarez of Puerto Rico stepped in to replace Banks but failed a medical on Friday and a clash with Norwich's former heavyweight world champion Herbie Hide fell through.
I controlled it and I did what I wanted
Hide appeared to have agreed to the fight as recently as Tuesday but the following day he could not be contacted.
Maccarinelli dropped Ellis inside the first minute with two hurtful body shots that forced his opponent onto one knee.
Ellis almost touched down again before one more venomous left hook to the ribs - Maccarinelli's most effective shot - sent him to the canvas for a second time.
The 34-year-old Ellis was clearly out of his depth as Maccarinelli smashed a right hand through his guard and finished the contest with another left to the body.
"In the second round I took control a bit," said Maccarinelli.
"I used the jab a bit more, used a bit more boxing and my power is such - my boxing is such - I knocked him out.
"Fair play to Matthew Ellis, he took a lot of heavy hits. I fought a much bigger guy, someone I didn't know too much about, but I controlled it and I did what I wanted."