UK light heavyweight Buatsi earned a win yet unimpressive debut to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But the challenger had his moments, landing some telling individual punches in a contest where the techniques failed to mesh, with constant grabbing spoiling the action.
The officials judged it 96-94 to the winner, with the third a even score.
"It wasn't my finest performance but what do champions do? They succeed," the victor stated in the arena as he was faced negative reactions from the crowd.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts thought Parker, thirty-one, deserved the win but the contender suffered the second loss of his 28-bout professional journey.
Buatsi Claims Triumph in Uneventful Affair
The fighter's advancement has slowed in the past few years through contract problems and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what seems like a final roll of the dice - under recent support.
He started carefully, with both competitors willing to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second fight at light heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a solid defense to edge the cleaner stanzas.
The audience's tolerance diminished amid frequent holding, with Parker falling to the floor several times during close exchanges.
Parker closed well, but multiple periods were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels Manchester Derby Contest
In the co-main event, Arthur defeated Rea by divided decision in a outstanding all-Manchester contest to capture the European light heavyweight belt.
The arena became quiet for a profoundly moving tribute prior to the bout as ten bells tolled in remembrance of the city's native Hatton, who died at age 46 in last month.
It was the initial significant broadcast fight night in the location since Hatton's death. As the final chime faded, the stillness transitioned to a chant of "there's just one Ricky Hatton".
The fighting within the ring matched the feeling. The eventual winner was floored by a left hook directly to the jaw in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red shorts of Arthur soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up soon, significant bruising forming under his face as the fighters landed powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with powerful upward punches as the action hardly diminished over 12 rounds.
The victor narrowly won the result with judges scorecards of draw, 115-113 and wider gap, but each competitor were persistent and full of heart, exactly what their inspiration Hatton embodied.
