British light heavyweight Buatsi earned a win yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close ten-round bout at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the styles didn't complement each other, with constant grabbing marring the contest.
The scoring judges had it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest display but how do champions respond? They prevail," the victor said in the ring as he was met by disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt the challenger, 31, should have been awarded the decision but the British boxer experienced the second loss of his 28-fight professional journey.
The Champion Earns Victory in Dull Encounter
The fighter's advancement has slowed in recent years through management issues and considerable time of lack of fights.
Once tipped as the next star of British boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with both competitors ready to overcommit in a cagey initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second appearance at light heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who utilized a tight guard to edge the better rounds.
The spectators' acceptance wore thin during frequent holding, with Parker falling to the floor various instances during close exchanges.
Parker closed well, but multiple periods were challenging to assess. However, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific Manchester vs Manchester contest to secure the continental belt.
The arena grew hushed for a deeply poignant tribute ahead of the contest as a bell ceremony rang in honor of the city's native Hatton, who passed away at age 46 in last month.
It was the premier televised fight night in the location since Hatton's death. As the last bell faded, the quiet gave way to a shout of "only one Hatton".
The competition during the bout equaled the feeling. The eventual winner was knocked down by a significant blow squarely on the chin in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured early, significant bruising developing under his eye as the duo exchanged powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor edged the decision with scoring tallies of even score, narrow lead and clearer margin, but each competitor were determined and courageous, exactly what their idol Hatton stood for.
