Alexander the Great was Saturday night.

Whether Devon Alexander really is great remains to be seen but the case he made for himself at the Mohegan Sun Arena was a big step, not only because it unified the WBC and IBF versions of the junior welterweight title but because he did it by destroying two-time champion Juan Urango in eight brutal and mostly one-sided rounds.

Alexander stopped the IBF champion at 1:12 of the eighth round, dropping him twice with sizzling right uppercuts, a punch he had warned him about in the fourth round but which the strong Colombian seemed powerless to do anything about but eat it until he’d had his fill. That came the second time he arose on wobbly legs, his mind chilled and his legs like overcooked spaghetti.

Referee Benji Estevez took one look at Urango after he’d pushed himself up off the floor for the second time in round eight and saw no reason to take a second one. Instead he looked at Urango’s seconds and said, “Come get him.’’

Alexander’s HBO debut could not have gone more swimmingly if he’d been Michael Phelps. His speed caused Urango no end of problems, making him difficult to hit as always but eventually luring Urango into spots trainer Kevin Cunningham had predicted he would end up in – which was to say in the free fire zone.

After stinging Urango repeatedly with his right jab, Alexander unloaded a right uppercut that caught Urango square and wobbled him in round 4. It was, as things turned out, a warning shot that went unheeded by the relentlessly resolute Urango.

In the end that would be the punch with which Alexander would finish him off but before he got around to that he had Urango spending most of his time following him around to no good end. To his credit, Urango (22-3-1, 17 KO) kept trying to find openings that closed too quickly for him to react, pressuring Alexander by constantly walking forward. That strategy was exactly what Cunningham expected and his game plan to negate it was perfectly executed by the 23-year-old Alexander.

“We had worked on it the whole camp,’’ Cunningham said of the uppercuts that eventually closed the show for his fighter. “That was the magic shot. I just saw how he plods forward and leans forward and figured you could catch him with the uppercut. I told Devon to throw the uppercut, and he heard me.  We used speed to set up the power.”

Alexander (20-0, 13) did just that and the results were surprisingly concussive against a guy who had never been stopped. While Alexander has long been considered a slick boxer with fast hands and feet his power has never been something that caused much of a stir. In the end it still may not but Saturday night it was on full display and Urango, who many consider to be among the physically strongest junior welterweights in the world, could not stand up to it.

“My coach told me to stay focused when Urango started bleeding [from the nose in the third round],’’ Alexander said. “My coach said, ‘Don’t stand there and get hit.’ As long as I’m moving he couldn’t touch me. His punches did not hurt at all.  I was surprised by that.  Speed kills everything and that’s what I have.’’

After what he did to Urango and former world champion Junior Witter before him (making him retire on his stool after the eighth round to win the then vacant WBC title), Alexander has begun to make a statement about who he is as well as what he has. That process is ongoing and will require he continue to not only win but to dominate the way he did against Urango if he is to become what his nickname has long claimed he will become but promoter Don King, never one to bypass a chance at bombast, declared loudly, “He’s not a star, he’s a superstar!’’

Not yet but King intends to bring him back to his hometown of St. Louis this summer to very likely face two-time world champion Zab Judah in what King has to hope is not a replay of a similar 2005 fight there between Judah and Alexander’s then stablemate Cory Spinks.

That fight attracted over 20,000 fans but Judah exposed Spinks’ weaknesses and stopped him in nine rounds to claim the unified welterweight title. Judah (38-6, 26 KO) has since said he’s returning to 140 pounds and King hopes to match him with Alexander and bill it as a night of revenge for St. Louis.

Judah took the welterweight title from Spinks that night but his career has been in decline ever since. Judah is 5-4-1 since that victory and he has lost every major fight he’s been in, and in ever declining fashion. He was beaten by Carlos Baldomir and Floyd Mayweather, Jr. by decision and stopped by Miguel Cotto and Joshua Clottey before abandoning the welterweight division and returning to 140.

Yet Judah was at ringside and claimed to be only moderately impressed with Alexander, insisting that while he has obvious skills they do not compare to his own. Time will tell about that but there are now five years and a world of difference between Alexander and Judah. One fighter is a young man on the rise. The other, a fading one on the decline.

Still, it will be another steppingstone for Alexander on the way to his true test, a unifying showdown with the best junior welterweight in the world – Timothy Bradley. Unless, of course, the best junior welterweight in the world turns out to be Alexander the Great simply because he is what we think he is – great indeed.

“I can beat anyone,’’ the wide-smiling Alexander said after stopping Urango. “Zab, Timothy Bradley. You name it. I want to come back to St. Louis and sell out the Scottrade center.  I’m coming back to good old St. Lou with two world titles.  This is sweet, very sweet.”

Saturday night so was Devon Alexander, sweet and vicious and very, very good.