UK light heavyweight Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, landing some telling individual punches in a contest where the approaches failed to mesh, with frequent clinching disrupting the action.
Two judges scored it 96-94 to the winner, with the final judge a even score.
"It wasn't my best display but what defines champions? They succeed," Buatsi commented in the ringside as he was greeted with boos from the crowd.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers believed Parker, 31, merited the victory but the British boxer endured the second loss of his 28-match career.
Buatsi Claims Victory in Dull Encounter
His career development has stalled in recent years through management issues and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to realize his potential - maybe in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter willing to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who worked behind a protective stance to edge the better periods.
The audience's tolerance decreased because of regular grabbing, with Parker falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Battle
In the co-main event, Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester battle to win the continental title.
The stadium became quiet for a profoundly moving homage ahead of the contest as a bell ceremony rang in memory of Manchester's own Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised match card in the location since Hatton's passing. As the concluding sound faded, the quiet became a shout of "there's just one Ricky Hatton".
The competition during the bout reflected the sentiment. The eventual winner was floored by a powerful punch directly to the chin in the second round, standing uncertainly to his feet on the referee's count.
But the traditional red equipment of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was marked up quickly, noticeable damage forming under his orbital area as the fighters landed hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
Arthur narrowly won the result with scoring tallies of 114-114, close margin and wider gap, but the two athletes were relentless and brave, everything their hero Hatton embodied.
