UK light heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a close ten-round bout at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful individual punches in a fight where the techniques didn't complement each other, with frequent clinching spoiling the contest.
The officials scored it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my finest performance but how do champions respond? They succeed," the victor said in the ringside as he was greeted with boos from the spectators.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the decision but the contender experienced the second setback of his 28-match professional journey.
The Champion Earns Victory in Slow Affair
Buatsi's progress has plateaued in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - possibly in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors ready to overcommit in a tentative opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second bout at light heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who operated with a protective stance to narrowly win the better stanzas.
The crowd's patience wore thin amid constant clinching, with the challenger going down multiple occasions during grappling.
Parker ended stronger, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a excellent local rivalry fight to secure the European light-heavyweight title.
The venue grew hushed for a extremely emotional memorial before the fight as a bell ceremony tolled in honor of the city's native Hatton, who died aged 46 in recently.
It was the first major televised fight night in the city since Hatton's passing. As the final chime disappeared, the silence became a chant of "there's just one Hatton".
The action during the bout equaled the feeling. Arthur was knocked down by a left hook flush on the face in the second round, rising shakily to his position on the count of eight.
But the traditional red shorts of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was marked up soon, significant bruising appearing under his eye as the duo exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over 12 rounds.
The victor edged the verdict with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were determined and brave, exactly what their inspiration the legend stood for.
