British light heavyweight Buatsi earned a win yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a tight 10-round bout at the boxing arena.
But the challenger had his moments, landing some telling individual punches in a match where the techniques failed to mesh, with frequent clinching disrupting the action.
The scoring judges judged it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my finest performance but what do champions do? They succeed," Buatsi said in the arena as he was met by boos from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers thought Parker, thirty-one, should have been awarded the victory but the contender endured the second defeat of his 28-bout career.
The Champion Claims Win in Dull Encounter
His career development has plateaued in the past few years through promotional disputes and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors willing to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner rounds.
The crowd's patience diminished amid constant clinching, with the challenger falling to the floor several times during grappling.
Parker closed well, but many rounds were hard to judge. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Inspires All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to win the European light-heavyweight belt.
The arena fell silent for a deeply poignant memorial prior to the bout as 10 bells tolled in remembrance of local hero Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the city since Hatton's death. As the final chime faded, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting during the bout equaled the feeling. The eventual winner was knocked down by a powerful punch directly to the chin in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured quickly, noticeable damage appearing under his face as the fighters landed powerful shots.
Rea, 27, connected with strong blows but the champion, 34, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
Arthur edged the verdict with scoring tallies of even score, close margin and 115-112, but each competitor were relentless and full of heart, exactly what their inspiration the legend stood for.
