UK light heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a competitive 10-round contest at the boxing arena.
But the challenger had his moments, landing some telling individual punches in a contest where the approaches never quite clicked, with frequent clinching marring the contest.
The officials judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my finest performance but what defines champions? They win," Buatsi commented in the arena as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought the challenger, 31, deserved the victory but the contender endured the second defeat of his 28-match professional journey.
Buatsi Earns Triumph in Dull Encounter
Buatsi's progress has stalled in the past few years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors ready to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second bout at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who operated with a solid defense to narrowly win the better stanzas.
The spectators' acceptance wore thin during constant clinching, with Parker falling to the floor several times during close exchanges.
Parker ended stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Hatton Homage Fuels Local Rivalry Battle
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent local rivalry fight to win the European light heavyweight title.
The stadium grew hushed for a profoundly moving memorial before the fight as a bell ceremony sounded in honor of local hero Hatton, who died 46 years old in September.
It was the premier televised boxing event in the urban center since Hatton's passing. As the final chime faded, the stillness became a chant of "there's only one Ricky Hatton".
The competition inside the ropes reflected the feeling. Arthur was knocked down by a powerful punch directly to the chin in the early round, rising shakily to his feet on the count of eight.
But the traditional red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was injured soon, heavy swelling appearing under his face as the pair traded punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity rarely dropped over the full distance.
Arthur narrowly won the result with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were determined and courageous, everything their inspiration the legend represented.
