UK light-heavyweight Buatsi made a winning yet underwhelming debut to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a fight where the styles didn't complement each other, with constant grabbing marring the contest.
The scoring judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my best showing but what defines champions? They succeed," Buatsi said in the arena as he was met by negative reactions from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the win but the Derbyshire fighter suffered the second loss of his 28-fight career.
The Champion Claims Win in Slow Match
Buatsi's progress has slowed in recent times through management issues and extended periods of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under recent support.
He started carefully, with neither fighter ready to overcommit in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who operated with a protective stance to narrowly win the cleaner periods.
The crowd's patience decreased amid constant clinching, with the challenger going down several times during close exchanges.
The underdog closed well, but several stanzas were hard to judge. However, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur defeated Rea by split-decision in a outstanding Manchester vs Manchester battle to capture the European light-heavyweight title.
The stadium fell silent for a profoundly moving tribute before the fight as 10 bells sounded in memory of local hero Ricky Hatton, who died at age 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime ended, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The action within the ring matched the sentiment. The eventual winner was floored by a left hook squarely on the jaw in the initial stage, standing uncertainly to his footing on the referee's count.
But the traditional red attire of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, noticeable damage appearing under his orbital area as the pair exchanged punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the result with scoring tallies of 114-114, narrow lead and clearer margin, but both fighters were persistent and full of heart, exactly what their idol the legend embodied.
