British light-heavyweight Buatsi earned a win yet underwhelming debut to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive ten-round fight at the Manchester venue.
But Parker found success, connecting with powerful single shots in a fight where the techniques never quite clicked, with frequent clinching marring the action.
The officials had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi said in the ring as he was greeted with disapproval from the audience.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th career victory.
Several boxing experts thought the challenger, thirty-one, should have been awarded the win but the contender experienced the second defeat of his 28-fight professional journey.
The Champion Claims Triumph in Uneventful Affair
Buatsi's progress has slowed in recent times through management issues and long spells of lack of fights.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - maybe in what seems like a last chance - under fresh management.
He began cautiously, with neither fighter willing to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who operated with a protective stance to barely take the cleaner rounds.
The audience's tolerance wore thin amid constant clinching, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, ex-champion the boxing analyst - working with Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Motivates Manchester Derby Contest
In the co-main event, Lyndon Arthur beat Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to win the European light heavyweight championship.
The stadium grew hushed for a profoundly moving memorial prior to the bout as ten bells sounded in memory of local hero Hatton, who succumbed aged 46 in last month.
It was the first major televised fight night in the city since Hatton's death. As the last bell ended, the silence became a shout of "there's only one Ricky Hatton".
The action inside the ropes reflected the emotion. Arthur was floored by a powerful punch flush on the chin in the second round, getting up unsteadily to his footing on the referee's count.
But the traditional red attire of Arthur soon came forward again. Across the ring, the opponent - in competitive blue - was damaged soon, noticeable damage forming under his face as the fighters landed punishing blows.
Rea, twenty-seven, landed power punches but the champion, 34, matched the intensity with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur barely secured the result with scoring tallies of 114-114, narrow lead and wider gap, but both fighters were determined and full of heart, exactly what their hero the legend stood for.
