British light heavyweight Buatsi earned a win yet unimpressive start to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a close ten-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a match where the techniques never quite clicked, with excessive holding marring the action.
The officials scored it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor commented in the arena as he was met by disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers believed the challenger, 31, should have been awarded the victory but the contender endured the second setback of his 28-match career.
Buatsi Claims Victory in Dull Match
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now stands trying to realize his potential - perhaps in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors willing to be aggressive in a calculated initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was competing in only his second appearance at light heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to edge the better rounds.
The audience's tolerance diminished amid constant clinching, with the challenger falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Hatton Memorial Motivates All-Manchester Fight
In the secondary fight, Arthur beat Rea by close verdict in a terrific all-Manchester battle to win the continental belt.
The stadium became quiet for a extremely emotional homage prior to the bout as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who died at age 46 in recently.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell ended, the stillness gave way to a chant of "there's just one Hatton".
The action inside the ropes matched the feeling. The eventual winner was floored by a left hook squarely on the chin in the early round, getting up unsteadily to his position on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his eye as the duo traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the pace rarely dropped over the full distance.
The victor barely secured the result with scoring tallies of even score, 115-113 and 115-112, but each competitor were determined and full of heart, everything their inspiration Hatton embodied.
