British light-heavyweight Buatsi secured a victory yet underwhelming start to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a fight where the styles failed to mesh, with excessive holding marring the action.
The scoring judges scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi said in the ring as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers felt the challenger, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-bout career.
Buatsi Earns Victory in Slow Affair
His career development has plateaued in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who operated with a protective stance to barely take the better stanzas.
The crowd's patience decreased amid frequent holding, with Parker falling to the floor multiple occasions during grappling.
Parker closed well, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Hatton Memorial Fuels All-Manchester Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a terrific Manchester vs Manchester fight to capture the European light heavyweight championship.
The stadium grew hushed for a extremely emotional homage prior to the bout as ten bells tolled in honor of Manchester's own Hatton, who died aged 46 in last month.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound disappeared, the stillness transitioned to a roar of "there's just one Hatton".
The competition during the bout reflected the feeling. Arthur was floored by a significant blow flush on the jaw in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was marked up early, heavy swelling appearing under his orbital area as the pair landed hard punches.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the pace hardly diminished over 12 rounds.
The victor edged the verdict with judges scorecards of draw, close margin and 115-112, but the two athletes were persistent and brave, exactly what their hero the legend embodied.
