British light heavyweight Buatsi earned a win yet underwhelming beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a split decision in a close 10-round contest at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a match where the techniques failed to mesh, with frequent clinching disrupting the action.
The scoring judges judged it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They win," the victor commented in the arena as he was greeted with boos from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Various analysts thought the challenger, 31, deserved the decision but the contender experienced the second setback of his 28-fight career.
The Champion Secures Triumph in Uneventful Affair
Buatsi's progress has stalled in recent years through management issues and long spells of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared to take risks in a cagey initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second bout at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who operated with a solid defense to barely take the cleaner rounds.
The spectators' acceptance wore thin amid frequent holding, with Parker going down multiple occasions during grappling.
The underdog ended stronger, but many rounds were difficult to score. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor advances, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Inspires All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a excellent all-Manchester fight to secure the European light heavyweight belt.
The venue grew hushed for a extremely emotional homage prior to the bout as 10 bells sounded in memory of local hero Hatton, who died 46 years old in September.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the final chime faded, the silence gave way to a shout of "only one Ricky Hatton".
The action within the ring reflected the emotion. Arthur was knocked down by a powerful punch squarely on the chin in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up quickly, noticeable damage appearing under his orbital area as the pair landed hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
The victor narrowly won the result with judges scorecards of even score, close margin and clearer margin, but both fighters were persistent and brave, everything their inspiration Hatton embodied.
