UK light heavyweight Buatsi made a winning yet disappointing start to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
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 the challenger had his moments, landing some telling individual punches in a match where the techniques didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but what defines champions? They succeed," the victor commented in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers felt the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter experienced the second setback of his 28-bout professional journey.
The Champion Earns Victory in Uneventful Encounter
His career development has plateaued in recent times through management issues and extended periods of lack of fights.
Previously predicted as the future of the British fight scene, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers prepared to be aggressive in a tentative early stages.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second fight at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to edge the better rounds.
The audience's tolerance wore thin because of constant clinching, with the challenger falling to the floor several times during grappling.
The underdog closed well, but multiple periods were difficult to score. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur overcame Rea by divided decision in a excellent all-Manchester battle to secure the European light heavyweight belt.
The stadium grew hushed for a extremely emotional memorial prior to the bout as 10 bells rang in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in September.
It was the first major televised match card in the location since Hatton's death. As the final chime faded, the silence became a chant of "only one Ricky Hatton".
The fighting within the ring reflected the feeling. The eventual winner was floored by a powerful punch flush on the chin in the initial stage, rising shakily to his feet on the count of eight.
But the traditional red attire of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was marked up early, noticeable damage appearing under his orbital area as the duo traded hard punches.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the action hardly diminished over the full distance.
Arthur edged the verdict with official scores of draw, narrow lead and 115-112, but each competitor were determined and brave, all the qualities their idol the legend represented.
