British light-heavyweight Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight 10-round contest at the boxing arena.
But the challenger found success, landing some telling clean blows in a contest where the techniques didn't complement each other, with frequent clinching marring the contest.
Two judges had it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest performance but what do champions do? They win," the victor commented in the ringside as he was met by negative reactions from the crowd.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Various analysts thought Parker, thirty-one, deserved the decision but the Derbyshire fighter endured the second setback of his 28-fight career.
The Champion Claims Triumph in Dull Affair
Buatsi's progress has stalled in recent times through management issues and extended periods of lack of fights.
Once tipped as the future of British boxing, he now finds himself trying to fulfil that early promise - maybe in what feels like a last chance - under fresh management.
He started carefully, with the two boxers willing to take risks in a tentative early stages.
Parker, 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 bout at the higher weight class.
By the fight's midpoint, Parker had kept it close, creating difficulties for Buatsi, who operated with a tight guard to edge the better rounds.
The crowd's patience wore thin during frequent holding, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were hard to judge. However, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester contest to win the European light-heavyweight belt.
The venue fell silent for a extremely emotional homage prior to the bout as a bell ceremony tolled in honor of Manchester's own Ricky Hatton, who passed away 46 years old in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the silence gave way to a shout of "there's only one Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was knocked down by a left hook flush on the jaw in the second round, standing uncertainly to his footing on the eight count.
But the red-colored attire of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was damaged soon, heavy swelling forming under his face as the duo landed powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
The victor narrowly won the decision with judges scorecards of 114-114, narrow lead and 115-112, but each competitor were relentless and full of heart, all the qualities their inspiration the legend represented.
