UK light heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive ten-round contest at the boxing arena.
But the challenger found success, delivering effective single shots in a fight where the styles never quite clicked, with excessive holding spoiling the contest.
The scoring judges scored it 96-94 to Buatsi, with the third a even score.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi commented in the ringside as he was faced negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, merited the win but the British boxer suffered the second setback of his 28-match career.
Buatsi Secures Win in Dull Affair
The fighter's advancement has slowed in recent years through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers prepared to be aggressive in a tentative initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, making life awkward for the favorite, who utilized a solid defense to barely take the better periods.
The spectators' acceptance diminished amid frequent holding, with Parker falling to the floor multiple occasions during clinches.
The underdog ended stronger, but many rounds were difficult to score. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still seems difficult.
Hatton Memorial Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a excellent local rivalry fight to capture the continental title.
The stadium grew hushed for a deeply poignant memorial ahead of the contest as a bell ceremony rang in remembrance of the city's native Hatton, who died 46 years old in recently.
It was the first major televised match card in the urban center since Hatton's death. As the final chime ended, the stillness gave way to a roar of "there's just one Ricky Hatton".
The action inside the ropes reflected the sentiment. The eventual winner was knocked down by a left hook directly to the jaw in the initial stage, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, noticeable damage forming under his eye as the pair exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the decision with scoring tallies of draw, 115-113 and clearer margin, but the two athletes were relentless and brave, everything their hero Hatton embodied.
