UK light-heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the styles failed to mesh, with constant grabbing disrupting the fight.
The officials had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They prevail," the victor stated in the ring as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in February - to claim a 20th pro success.
Various analysts believed the challenger, thirty-one, deserved the win but the Derbyshire fighter suffered the second defeat of his 28-bout professional journey.
Buatsi Secures Win in Uneventful Encounter
His career development has plateaued in recent years through management issues and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under recent support.
He started carefully, with the two boxers willing to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was participating in his second appearance at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a tight guard to barely take the more effective stanzas.
The spectators' acceptance wore thin during frequent holding, with the challenger going down several times during grappling.
The underdog closed well, but several stanzas were difficult to score. However, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Fuels Manchester Derby Battle
In the co-main event, Arthur defeated Bradley Rea by split-decision in a outstanding local rivalry contest to secure the European light-heavyweight championship.
The venue grew hushed for a extremely emotional tribute before the fight as ten bells sounded in memory of Manchester's own Hatton, who succumbed 46 years old in September.
It was the first major televised boxing event in the city since Hatton's passing. As the last bell ended, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The competition during the bout matched the sentiment. Arthur was floored by a left hook flush on 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. On the opposite side, Rea - in opposing blue - was marked up early, noticeable damage developing under his face as the fighters landed punishing blows.
Rea, 27, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace hardly diminished over the full distance.
The victor narrowly won the result with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were persistent and full of heart, all the qualities their inspiration the legend stood for.
