UK light-heavyweight Buatsi earned a win yet unimpressive beginning to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round bout at the Manchester venue.
But Parker landed significant shots, connecting with powerful single shots in a match where the styles didn't complement each other, with excessive holding spoiling the contest.
The officials had it 96-94 to the winner, with the final judge a even score.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi said in the arena as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with Callum Smith in February - to earn a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the decision but the British boxer suffered the second loss of his 28-match career.
The Champion Secures Win in Slow Affair
The fighter's advancement has slowed in recent years through management issues and extended periods of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to realize his potential - possibly in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors willing to overcommit in a tentative initial rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a protective stance to barely take the more effective stanzas.
The crowd's patience decreased during regular grabbing, with Parker falling to the floor several times during close exchanges.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the presence of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels Manchester Derby Fight
In the secondary fight, Arthur defeated Rea by close verdict in a excellent Manchester vs Manchester fight to capture the European light-heavyweight championship.
The venue grew hushed for a deeply poignant homage ahead of the contest as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime disappeared, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was floored by a left hook flush on the chin in the second round, rising shakily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, the opponent - in opposing blue - was damaged quickly, significant bruising forming under his eye as the pair exchanged hard punches.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
Arthur edged the verdict with judges scorecards of 114-114, close margin and wider gap, but the two athletes were determined and full of heart, everything their idol Hatton represented.
