British light-heavyweight Buatsi made a winning yet unimpressive debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a contest where the approaches never quite clicked, with constant grabbing marring the action.
The officials scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what defines champions? They succeed," the victor commented in the ringside as he was met by boos from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Several boxing experts thought the challenger, thirty-one, should have been awarded the win but the British boxer endured the second defeat of his 28-match career.
Buatsi Secures Victory in Uneventful Encounter
Buatsi's progress has stalled in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to take risks in a cagey opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who worked behind a solid defense to edge the better stanzas.
The spectators' acceptance diminished during frequent holding, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker finished the stronger, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the co-main event, Arthur defeated Rea by split-decision in a terrific all-Manchester battle to capture the European light-heavyweight title.
The venue grew hushed for a extremely emotional memorial ahead of the contest as 10 bells sounded in remembrance of Manchester's own Hatton, who succumbed at age 46 in recently.
It was the premier televised match card in the city since Hatton's passing. As the concluding sound disappeared, the quiet transitioned to a roar of "there's only one Ricky Hatton".
The action during the bout reflected the feeling. Arthur was floored by a left hook directly to the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red equipment of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was damaged quickly, heavy swelling appearing under his orbital area as the fighters exchanged powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the pace hardly diminished over 12 rounds.
Arthur barely secured the result with official scores of 114-114, 115-113 and 115-112, but each competitor were persistent and brave, exactly what their idol Hatton stood for.
