British light heavyweight Buatsi earned a win yet underwhelming beginning to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive ten-round fight at the boxing arena.
But the challenger landed significant shots, connecting with powerful single shots in a match where the techniques failed to mesh, with constant grabbing disrupting the action.
Two judges had it 96-94 for to the winner, with the third a even score.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the arena as he was faced boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second setback of his 28-fight career.
The Champion Earns Win in Slow Match
The fighter's advancement has slowed in recent times through management issues and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now stands trying to realize his potential - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who operated with a protective stance to edge the more effective stanzas.
The audience's tolerance diminished during regular grabbing, with the challenger falling to the floor multiple occasions during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just one round.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Fuels Manchester Derby Fight
In the secondary fight, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry contest to win the European light heavyweight championship.
The stadium fell silent for a profoundly moving homage before the fight as a bell ceremony sounded in memory of the city's native Hatton, who succumbed 46 years old in September.
It was the first major televised fight night in the city since Hatton's passing. As the concluding sound faded, the stillness became a shout of "there's just one Ricky Hatton".
The action inside the ropes matched the feeling. Arthur was floored by a left hook directly to the face in the initial stage, rising shakily to his position on the eight count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was damaged soon, heavy swelling developing under his eye as the fighters exchanged hard punches.
Rea, 27, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the action seldom decreased over 12 rounds.
The victor narrowly won the decision with official scores of draw, close margin and wider gap, but both fighters were determined and brave, everything their idol Hatton stood for.
