British light heavyweight Buatsi secured a victory yet underwhelming debut to his career under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a close ten-round contest at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a contest where the approaches failed to mesh, with constant grabbing spoiling the fight.
The officials judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi said in the arena as he was greeted with negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the win but the British boxer suffered the second loss of his 28-bout professional journey.
The Champion Secures Victory in Uneventful Match
Buatsi's progress has plateaued in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to realize his potential - possibly in what seems like a last chance - under fresh management.
He began cautiously, with neither fighter ready to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who worked behind a solid defense to edge the more effective periods.
The audience's tolerance diminished amid frequent holding, with the challenger slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but several stanzas were hard to judge. However, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent all-Manchester fight to secure the European light-heavyweight title.
The stadium became quiet for a profoundly moving tribute before the fight as ten bells tolled in remembrance of Manchester's own Hatton, who passed away aged 46 in last month.
It was the premier televised boxing event in the city since the passing of Hatton. As the last bell disappeared, the stillness transitioned to a roar of "there's just one Ricky Hatton".
The fighting within the ring matched the emotion. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the initial stage, rising shakily to his footing on the referee's count.
But the traditional red shorts of Arthur soon advanced again. Across the ring, Rea - in opposing blue - was damaged quickly, heavy swelling forming under his face as the duo landed hard punches.
Rea, 27, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over the full distance.
The victor barely secured the verdict with judges scorecards of draw, close margin and wider gap, but both fighters were persistent and courageous, all the qualities their inspiration the legend represented.
