UK light-heavyweight Buatsi made a winning yet underwhelming debut to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a split decision in a competitive 10-round fight at the Manchester venue.
But Parker found success, landing some telling individual punches in a contest where the styles didn't complement each other, with constant grabbing marring the fight.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest showing but how do champions respond? They succeed," Buatsi said in the ringside as he was met by disapproval from the spectators.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the victory but the contender experienced the second setback of his 28-bout career.
The Champion Earns Win in Slow Affair
The fighter's advancement has plateaued in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under new promotional backing.
He began cautiously, with neither fighter prepared to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second bout at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to barely take the cleaner rounds.
The audience's tolerance diminished amid frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. Nevertheless, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Homage Fuels Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by divided decision in a terrific local rivalry fight to win the European light-heavyweight title.
The venue grew hushed for a profoundly moving tribute prior to the bout as a bell ceremony tolled in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the first major televised match card in the city since the passing of Hatton. As the final chime disappeared, the silence gave way to a shout of "only one Hatton".
The action inside the ropes equaled the emotion. Arthur was sent to the canvas by a significant blow squarely on the chin in the second round, standing uncertainly to his position on the referee's count.
But the traditional red shorts of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was marked up early, heavy swelling forming under his face as the duo traded hard punches.
Rea, 27, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action hardly diminished over the full distance.
The victor narrowly won the result with official scores of draw, narrow lead and 115-112, but each competitor were persistent and brave, all the qualities their hero the legend stood for.
