British light-heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a majority decision in a competitive 10-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a contest where the techniques didn't complement each other, with excessive holding spoiling the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi commented in the ringside as he was faced boos from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Several boxing experts felt Parker, thirty-one, merited the win but the British boxer suffered the second loss of his 28-bout career.
The Champion Claims Triumph in Uneventful Affair
His career development has slowed in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who worked behind a tight guard to barely take the more effective rounds.
The crowd's patience wore thin because of frequent holding, with Parker falling to the floor various instances during clinches.
The underdog ended stronger, but several stanzas were hard to judge. However, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor moves on, but with the caliber of power puncher Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry battle to win the continental title.
The arena became quiet for a profoundly moving tribute prior to the bout as ten bells sounded in remembrance of Manchester's own Hatton, who died aged 46 in last month.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the final chime faded, the stillness transitioned to a shout of "there's only one Hatton".
The action inside the ropes matched the sentiment. Arthur was knocked down by a significant blow squarely on the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the Manchester United-red shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up quickly, heavy swelling forming under his orbital area as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur edged the verdict with scoring tallies of even score, narrow lead and wider gap, but the two athletes were persistent and brave, everything their hero Hatton stood for.
