British light heavyweight Buatsi made a winning yet unimpressive start to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a competitive 10-round contest at the Co-op Live Arena.
But the challenger found success, connecting with powerful clean blows in a fight where the styles never quite clicked, with excessive holding spoiling the fight.
The officials scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my best performance but how do champions respond? They prevail," Buatsi commented in the ring as he was faced disapproval from the audience.
The British fighter returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to earn a 20th career victory.
Several boxing experts felt the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second loss of his 28-match career.
Buatsi Claims Victory in Uneventful Match
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now stands trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He started carefully, with both competitors ready to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to edge the more effective rounds.
The crowd's patience wore thin amid constant clinching, with Parker going down several times during clinches.
The underdog closed well, but several stanzas were hard to judge. However, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the supporting bout, Arthur beat Bradley Rea by close verdict in a outstanding all-Manchester fight to capture the continental championship.
The venue grew hushed for a deeply poignant memorial before the fight as 10 bells rang in remembrance of the city's native Ricky Hatton, who died aged 46 in last month.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime ended, the stillness transitioned to a shout of "only one Hatton".
The competition during the bout equaled the emotion. The eventual winner was sent to the canvas by a powerful punch directly to the chin in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was injured early, noticeable damage developing under his face as the duo landed powerful shots.
Rea, 27, landed power punches but Arthur, 34, matched the intensity with powerful upward punches as the action seldom decreased over the full distance.
The victor barely secured the decision with judges scorecards of draw, narrow lead and wider gap, but the two athletes were persistent and brave, exactly what their hero the legend represented.
