British light heavyweight Buatsi made a winning yet underwhelming beginning to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive ten-round fight at the boxing arena.
But the challenger had his moments, delivering effective single shots in a match where the styles didn't complement each other, with constant grabbing spoiling the fight.
The officials had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest showing but what do champions do? They win," the victor stated in the arena as he was greeted with negative reactions from the audience.
The Londoner bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to claim a 20th career victory.
Several boxing experts believed the challenger, thirty-one, should have been awarded the decision but the contender endured the second setback of his 28-bout professional journey.
Buatsi Claims Win in Slow Affair
The fighter's advancement has slowed in recent years through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under fresh management.
He began cautiously, with neither fighter willing to take risks in a calculated opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second fight at light heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who worked behind a solid defense to barely take the cleaner periods.
The audience's tolerance wore thin because of frequent holding, with Parker slipping to the canvas multiple occasions during grappling.
The underdog ended stronger, but multiple periods were difficult to score. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a terrific all-Manchester battle to secure the continental championship.
The stadium grew hushed for a profoundly moving tribute prior to the bout as ten bells sounded in honor of the city's native Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the last bell ended, the quiet became a chant of "there's only one Ricky Hatton".
The fighting within the ring equaled the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the face in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up early, significant bruising developing under his face as the duo landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the action seldom decreased over twelve rounds.
Arthur edged the verdict with scoring tallies of draw, 115-113 and 115-112, but each competitor were relentless and brave, all the qualities their idol Hatton stood for.
