UK light-heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a contest where the techniques never quite clicked, with frequent clinching marring the contest.
The scoring judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They prevail," the victor stated in the ring as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts believed Parker, 31, deserved the win but the contender endured the second defeat of his 28-match professional journey.
The Champion Earns Win in Dull Encounter
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of UK boxing, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a cagey initial rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who operated with a tight guard to barely take the better stanzas.
The audience's tolerance wore thin during frequent holding, with the challenger going down multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Fuels Local Rivalry Contest
In the co-main event, Arthur overcame Rea by split-decision in a excellent local rivalry fight to capture the European light-heavyweight championship.
The arena fell silent for a extremely emotional memorial ahead of the contest as a bell ceremony tolled in memory of local hero Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's passing. As the final chime ended, the stillness gave way to a chant of "only one Hatton".
The fighting during the bout matched the emotion. The eventual winner was floored by a powerful punch squarely on the chin in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was injured soon, significant bruising forming under his orbital area as the pair traded hard punches.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, 115-113 and wider gap, but the two athletes were determined and full of heart, everything their hero the legend represented.
