British light heavyweight Buatsi made a winning yet unimpressive start to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close 10-round contest at the Manchester venue.
But Parker had his moments, landing some telling single shots in a match where the styles never quite clicked, with constant grabbing marring the contest.
The scoring judges had it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my best showing but what do champions do? They prevail," the victor stated in the arena as he was met by disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th pro success.
Some ringside observers felt the challenger, thirty-one, deserved the decision but the British boxer suffered the second defeat of his 28-bout career.
Buatsi Secures Triumph in Slow Affair
His career development has slowed in recent times through management issues and long spells of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to realize his potential - possibly in what seems like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to overcommit in a cagey early stages.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for the favorite, who utilized a tight guard to barely take the more effective stanzas.
The audience's tolerance diminished because of frequent holding, with the challenger going down various instances during close exchanges.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires All-Manchester Battle
In the supporting bout, Arthur beat Rea by split-decision in a terrific all-Manchester battle to win the European light heavyweight championship.
The stadium became quiet for a deeply poignant memorial ahead of the contest as 10 bells sounded in remembrance of local hero Ricky Hatton, who died aged 46 in recently.
It was the first major televised fight night in the urban center since Hatton's passing. As the final chime disappeared, the quiet became a chant of "only one Hatton".
The fighting during the bout reflected the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the chin in the second round, standing uncertainly to his position on the referee's count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was marked up soon, noticeable damage developing under his eye as the fighters landed punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor barely secured the verdict with judges scorecards of 114-114, narrow lead and wider gap, but each competitor were determined and brave, everything their idol Hatton embodied.
