UK light-heavyweight Buatsi earned a win yet unimpressive start to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a tight 10-round bout at the Manchester venue.
But Parker found success, delivering effective single shots in a fight where the styles failed to mesh, with excessive holding disrupting the contest.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest display but how do champions respond? They win," the victor commented in the arena as he was met by boos from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to earn a 20th career victory.
Some ringside observers felt Parker, 31, merited the win but the contender suffered the second loss of his 28-match professional journey.
The Champion Secures Victory in Slow Encounter
Buatsi's progress has slowed in the past few years through management issues and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to realize his potential - possibly in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter prepared to overcommit in a calculated initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was participating in his second bout at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, making life awkward for the favorite, who utilized a tight guard to edge the cleaner periods.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas various instances during clinches.
Parker finished the stronger, but several stanzas were challenging to assess. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Memorial Fuels All-Manchester Fight
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to win the European light-heavyweight belt.
The stadium grew hushed for a profoundly moving homage prior to the bout as 10 bells rang in honor of the city's native Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the final chime ended, the quiet transitioned to a chant of "only one Hatton".
The competition during the bout matched the sentiment. Arthur was knocked down by a powerful punch directly to the chin in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored shorts of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was injured soon, heavy swelling developing under his orbital area as the duo exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with effective uppercuts as the action hardly diminished over twelve rounds.
The victor narrowly won the verdict with judges scorecards of draw, close margin and wider gap, but the two athletes were relentless and brave, everything their idol the legend represented.
