UK light-heavyweight Buatsi made a winning yet underwhelming start to life under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a competitive 10-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a contest where the approaches failed to mesh, with frequent clinching marring the action.
Two judges judged it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best performance but what defines champions? They win," the victor said in the arena as he was faced negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Various analysts thought Parker, thirty-one, deserved the victory but the contender experienced the second loss of his 28-bout career.
Buatsi Secures Triumph in Slow Match
The fighter's advancement has slowed in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a last chance - under new promotional backing.
He started carefully, with both competitors prepared to overcommit in a cagey initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to edge the more effective periods.
The crowd's patience decreased amid regular grabbing, with Parker falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were hard to judge. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Fight
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a outstanding Manchester vs Manchester contest to secure the European light heavyweight belt.
The venue became quiet for a deeply poignant tribute ahead of the contest as ten bells sounded in memory of local hero Hatton, who died at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound disappeared, the quiet transitioned to a roar of "there's just one Hatton".
The competition within the ring equaled the feeling. Arthur was floored by a powerful punch flush on the face in the initial stage, rising shakily to his feet on the referee's count.
But the Manchester United-red shorts of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was injured quickly, heavy swelling developing under his eye as the duo traded powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the verdict with judges scorecards of 114-114, close margin and 115-112, but the two athletes were persistent and courageous, all the qualities their hero the legend represented.
