British light-heavyweight Buatsi earned a win yet disappointing beginning to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the styles failed to mesh, with constant grabbing marring the action.
Two judges judged it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best performance but what defines champions? They succeed," the victor stated in the ring as he was faced disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Various analysts felt the challenger, 31, merited the win but the contender experienced the second loss of his 28-fight professional journey.
Buatsi Earns Triumph in Uneventful Match
Buatsi's progress has plateaued in recent years through promotional disputes and long spells of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who utilized a protective stance to edge the better rounds.
The spectators' acceptance wore thin amid regular grabbing, with the challenger falling to the floor various instances during clinches.
The underdog finished the stronger, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to win the European light heavyweight belt.
The venue fell silent for a profoundly moving homage ahead of the contest as ten bells sounded in remembrance of the city's native Hatton, who succumbed aged 46 in recently.
It was the first major televised match card in the city since Hatton's passing. As the last bell disappeared, the silence gave way to a shout of "only one Ricky Hatton".
The action inside the ropes reflected the feeling. Arthur was floored by a significant blow flush on the jaw in the second round, standing uncertainly to his footing on the eight count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was damaged early, heavy swelling appearing under his face as the pair exchanged punishing blows.
The challenger, 27, delivered effective strikes but the champion, 34, matched the intensity with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the decision with official scores of even score, 115-113 and clearer margin, but each competitor were relentless and full of heart, all the qualities their inspiration the legend stood for.
