British light-heavyweight Buatsi secured a victory yet disappointing beginning to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a match where the approaches never quite clicked, with constant grabbing disrupting the contest.
Two judges had it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my finest performance but how do champions respond? They win," the victor said in the ring 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 last winter - to claim a 20th career victory.
Some ringside observers believed Parker, 31, merited the decision but the contender endured the second loss of his 28-fight career.
The Champion Claims Victory in Slow Match
His career development has plateaued in recent years through management issues and long spells of inactivity.
Once tipped as the future of British boxing, he now stands trying to achieve expectations - perhaps in what feels like a last chance - under recent support.
He began cautiously, with the two boxers willing to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was participating in his second bout at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who utilized a solid defense to narrowly win the more effective rounds.
The spectators' acceptance wore thin amid regular grabbing, with the challenger going down various instances during grappling.
Parker finished the stronger, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry battle to capture the continental belt.
The venue fell silent for a extremely emotional memorial before the fight as ten bells tolled in memory of local hero Ricky Hatton, who died 46 years old in last month.
It was the initial significant broadcast fight night in the city since Hatton's passing. As the concluding sound faded, the silence transitioned to a roar of "there's only one Ricky Hatton".
The fighting inside the ropes equaled the emotion. The eventual winner was floored by a left hook flush on the face in the second round, rising shakily 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 marked up soon, significant bruising developing under his eye as the pair traded punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over twelve rounds.
The victor barely secured the result with scoring tallies of 114-114, narrow lead and clearer margin, but the two athletes were relentless and full of heart, all the qualities their hero Hatton represented.
