UK light-heavyweight Buatsi made a winning yet disappointing debut to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a competitive ten-round contest at the Manchester venue.
But Parker had his moments, delivering effective single shots in a contest where the styles didn't complement each other, with excessive holding spoiling the fight.
The officials scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best display but how do champions respond? They prevail," Buatsi said in the arena as he was greeted with disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Various analysts thought the challenger, thirty-one, merited the decision but the contender suffered the second loss of his 28-fight career.
The Champion Claims Win in Uneventful Encounter
His career development has stalled in recent times through management issues and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers willing to overcommit in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who utilized a tight guard to narrowly win the cleaner periods.
The crowd's patience diminished amid frequent holding, with the challenger slipping to the canvas several times during grappling.
The underdog ended stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Motivates All-Manchester Battle
In the supporting bout, Arthur defeated Rea by split-decision in a outstanding local rivalry fight to capture the continental title.
The arena became quiet for a profoundly moving memorial prior to the bout as ten bells sounded in remembrance of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the location since Hatton's passing. As the final chime ended, the quiet transitioned to a shout of "only one Ricky Hatton".
The competition during the bout matched the emotion. The eventual winner was floored by a powerful punch directly to the chin in the initial stage, standing uncertainly to his feet on the count of eight.
But the red-colored equipment of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his face as the fighters traded powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action rarely dropped over 12 rounds.
The victor narrowly won the verdict with judges scorecards of 114-114, narrow lead and 115-112, but both fighters were determined and full of heart, everything their inspiration the legend stood for.
