UK light-heavyweight Buatsi earned a win yet underwhelming start to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a judges' verdict in a tight ten-round fight at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a match where the approaches didn't complement each other, with constant grabbing spoiling the action.
The officials judged it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor said in the arena as he was faced boos from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, deserved the win but the contender endured the second setback of his 28-match career.
Buatsi Secures Victory in Slow Encounter
His career development has slowed in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to overcommit in a tentative initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who operated with a solid defense to edge the more effective stanzas.
The spectators' acceptance diminished during regular grabbing, with Parker falling to the floor multiple occasions during close exchanges.
The underdog closed well, but multiple periods were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Arthur overcame Rea by divided decision in a terrific all-Manchester battle to secure the continental championship.
The arena became quiet for a deeply poignant tribute ahead of the contest as 10 bells sounded in remembrance of local hero Hatton, who succumbed at age 46 in last month.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound faded, the quiet became a roar of "there's only one Hatton".
The fighting within the ring matched the feeling. Arthur was floored by a powerful punch squarely on the chin in the initial stage, rising shakily to his position on the referee's count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged soon, noticeable damage appearing under his face as the fighters traded hard punches.
The challenger, 27, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over the full distance.
Arthur barely secured the decision with official scores of even score, 115-113 and 115-112, but both fighters were relentless and full of heart, all the qualities their hero Hatton represented.
