British light heavyweight Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a match where the styles never quite clicked, with excessive holding spoiling the action.
Two judges had it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest display but what do champions do? They succeed," the victor commented in the ringside as he was greeted with negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers felt the challenger, 31, deserved the decision but the British boxer experienced the second loss of his 28-bout career.
Buatsi Secures Triumph in Slow Match
His career development has plateaued in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what feels like a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to take risks in a tentative early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for Buatsi, who operated with a tight guard to barely take the better periods.
The crowd's patience wore thin during regular grabbing, with the challenger falling to the floor several times during grappling.
Parker ended stronger, but many rounds were hard to judge. However, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a excellent local rivalry fight to win the European light-heavyweight belt.
The venue fell silent for a deeply poignant tribute ahead of the contest as ten bells tolled in honor of the city's native Ricky Hatton, who died 46 years old in recently.
It was the premier televised fight night in the urban center since Hatton's passing. As the last bell disappeared, the silence became a chant of "only one Hatton".
The fighting within the ring reflected the feeling. Arthur was knocked down by a left hook squarely on the face in the second round, standing uncertainly to his footing on the count of eight.
But the red-colored shorts of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was damaged soon, heavy swelling appearing under his eye as the duo exchanged powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur narrowly won the decision with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were relentless and courageous, everything their inspiration the legend represented.
