UK light heavyweight Buatsi earned a win yet unimpressive beginning to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a contest where the techniques didn't complement each other, with frequent clinching disrupting the contest.
Two judges had it 96-94 to the winner, with the third a 95-95.
"It wasn't my greatest performance but what defines champions? They prevail," Buatsi commented in the ring as he was faced disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Various analysts believed Parker, 31, should have been awarded the win but the British boxer suffered the second loss of his 28-match professional journey.
The Champion Earns Triumph in Dull Affair
The fighter's advancement has slowed in the past few years through management issues and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who operated with a tight guard to narrowly win the more effective rounds.
The crowd's patience decreased amid frequent holding, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but many rounds were difficult to score. However, previous titleholder Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Fuels Local Rivalry Fight
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry fight to capture the European light heavyweight title.
The arena fell silent for a extremely emotional homage prior to the bout as 10 bells rang in memory of Manchester's own Hatton, who succumbed at age 46 in September.
It was the first major televised boxing event in the location since the passing of Hatton. As the last bell disappeared, the stillness became a roar of "only one Ricky Hatton".
The action inside the ropes equaled the emotion. The eventual winner was floored by a significant blow flush on the chin in the initial stage, getting up unsteadily to his position on the eight count.
But the traditional red equipment of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was marked up soon, noticeable damage forming under his orbital area as the duo landed punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the action rarely dropped over the full distance.
Arthur barely secured the decision with scoring tallies of 114-114, narrow lead and wider gap, but each competitor were persistent and brave, everything their hero Hatton stood for.
