British light-heavyweight Buatsi earned a win yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger found success, delivering effective single shots in a match where the approaches didn't complement each other, with constant grabbing disrupting the fight.
The officials had it 96-94 to the winner, with the final judge a even score.
"It wasn't my best display but how do champions respond? They win," Buatsi said in the ringside as he was greeted with negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to earn a 20th pro success.
Various analysts felt the challenger, thirty-one, deserved the victory but the British boxer experienced the second loss of his 28-match professional journey.
The Champion Secures Win in Dull Match
Buatsi's progress has plateaued in recent years through management issues and long spells of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to realize his potential - maybe in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers prepared to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a tight guard to edge the better rounds.
The crowd's patience diminished amid frequent holding, with Parker going down various instances during close exchanges.
The underdog ended stronger, but multiple periods were difficult to score. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor moves on, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Hatton Homage Motivates Manchester Derby Contest
In the co-main event, Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester battle to secure the European light-heavyweight championship.
The arena became quiet for a extremely emotional tribute before the fight as ten bells tolled in honor of the city's native Ricky Hatton, who died at age 46 in September.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime ended, the quiet transitioned to a chant of "only one Hatton".
The action inside the ropes equaled the feeling. Arthur was sent to the canvas by a powerful punch squarely on the face in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red equipment of Arthur soon advanced again. On the opposite side, Rea - in competitive blue - was damaged quickly, noticeable damage appearing under his eye as the duo exchanged powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur edged the decision with scoring tallies of even score, 115-113 and wider gap, but each competitor were relentless and courageous, everything their inspiration the legend represented.
