UK light-heavyweight Buatsi earned a win yet unimpressive beginning to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive ten-round bout at the boxing arena.
But the challenger found success, connecting with powerful individual punches in a fight where the approaches failed to mesh, with constant grabbing disrupting the action.
Two judges judged it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest performance but what do champions do? They prevail," the victor commented in the ringside as he was faced boos from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts thought Parker, thirty-one, merited the victory but the British boxer experienced the second setback of his 28-fight career.
Buatsi Earns Win in Dull Affair
The fighter's advancement has slowed in recent years through contract problems and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - maybe in what seems like a ultimate opportunity - under fresh management.
He started carefully, with both competitors ready to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at the lower weight class 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, the underdog had kept it close, causing problems for the favorite, who worked behind a protective stance to edge the more effective rounds.
The crowd's patience decreased during regular grabbing, with the challenger going down several times during clinches.
The underdog closed well, but several stanzas were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor moves on, but with the presence of hard hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to win the continental belt.
The stadium became quiet for a profoundly moving homage before the fight as 10 bells rang in memory of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime ended, the quiet transitioned to a chant of "only one Hatton".
The fighting inside the ropes matched the feeling. Arthur was knocked down by a left hook directly to the chin in the second round, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his eye as the duo exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with official scores of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their idol Hatton stood for.
