UK light-heavyweight Buatsi secured a victory yet unimpressive start to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a close ten-round contest at the Manchester venue.
But the challenger found success, delivering effective single shots in a match where the techniques never quite clicked, with excessive holding spoiling the fight.
Two judges scored it 96-94 to the winner, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi stated in the ring as he was faced boos from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in February - to earn a 20th career victory.
Various analysts thought the challenger, 31, should have been awarded the win but the Derbyshire fighter experienced the second defeat of his 28-fight career.
Buatsi Earns Triumph in Slow Match
The fighter's advancement has stalled in the past few years through promotional disputes and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers prepared 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 breaking his hand during the bout, was making just his second bout at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the cleaner stanzas.
The crowd's patience wore thin during regular grabbing, with Parker going down several times during clinches.
Parker finished the stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Inspires Local Rivalry Contest
In the secondary fight, Arthur beat Rea by close verdict in a terrific all-Manchester contest to win the continental belt.
The arena fell silent for a extremely emotional memorial prior to the bout as a bell ceremony rang in memory of the city's native Hatton, who succumbed aged 46 in last month.
It was the premier televised fight night in the location since Hatton's death. As the concluding sound ended, the quiet gave way to a chant of "there's only one Hatton".
The competition during the bout equaled the sentiment. Arthur was sent to the canvas by a left hook flush on the chin in the early round, standing uncertainly to his position on the eight count.
But the traditional red attire of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was marked up early, significant bruising appearing under his face as the pair exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the intensity hardly diminished over 12 rounds.
The victor narrowly won the verdict with judges scorecards of draw, close margin and clearer margin, but both fighters were determined and full of heart, exactly what their hero the legend represented.
