British light-heavyweight Buatsi earned a win yet unimpressive debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a judges' verdict in a tight 10-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful single shots in a match where the techniques never quite clicked, with excessive holding spoiling the contest.
Two judges scored it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my greatest showing but what do champions do? They win," Buatsi said in the ringside as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his first professional defeat - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, merited the victory but the contender suffered the second loss of his 28-fight career.
The Champion Earns Triumph in Uneventful Affair
Buatsi's progress has slowed in recent times through contract problems and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers ready to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was making just his second fight at the higher weight class.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who operated with a solid defense to barely take the cleaner stanzas.
The spectators' acceptance decreased amid constant clinching, with Parker going down multiple occasions during grappling.
Parker closed well, but multiple periods were hard to judge. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor advances, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Tribute Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur overcame Rea by split-decision in a outstanding local rivalry contest to capture the continental championship.
The stadium fell silent for a extremely emotional homage prior to the bout as ten bells sounded in honor of Manchester's own Hatton, who died at age 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the last bell faded, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a powerful punch squarely on the face in the initial stage, rising shakily to his position on the count of eight.
But the traditional red attire of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was damaged early, significant bruising appearing under his orbital area as the duo exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action seldom decreased over the full distance.
Arthur edged the result with scoring tallies of 114-114, 115-113 and 115-112, but each competitor were determined and courageous, all the qualities their inspiration Hatton embodied.
