British light-heavyweight Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a close 10-round fight at the boxing arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the approaches never quite clicked, with constant grabbing spoiling the action.
The scoring judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi said in the ring as he was faced disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts believed the challenger, 31, deserved the win but the Derbyshire fighter suffered the second setback of his 28-fight career.
The Champion Claims Victory in Slow Encounter
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He started carefully, with the two boxers willing to overcommit in a tentative early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only 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 tight guard to edge the cleaner stanzas.
The crowd's patience wore thin because of constant clinching, with the challenger going down various instances during close exchanges.
Parker finished the stronger, but several stanzas were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Motivates Manchester Derby Contest
In the secondary fight, Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester fight to secure the continental championship.
The stadium fell silent for a deeply poignant homage prior to the bout as ten bells rang in memory of Manchester's own Hatton, who passed away aged 46 in recently.
It was the premier televised boxing event in the city since Hatton's death. As the final chime disappeared, the silence became a roar of "only one Hatton".
The competition inside the ropes equaled the feeling. Arthur was sent to the canvas by a left hook flush on the jaw in the second round, rising shakily to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was marked up quickly, noticeable damage forming under his orbital area as the duo exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
The victor narrowly won the decision with official scores of 114-114, 115-113 and clearer margin, but each competitor were persistent and brave, exactly what their hero Hatton stood for.
