British light heavyweight Buatsi made a winning yet unimpressive debut to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive 10-round bout at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a match where the techniques never quite clicked, with frequent clinching disrupting the contest.
The officials judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my best display but what do champions do? They succeed," Buatsi said in the arena as he was met by boos from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers thought Parker, thirty-one, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
Buatsi Claims Win in Dull Affair
Buatsi's progress has plateaued in recent times through management issues and considerable time of lack of fights.
Once tipped as the next star of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers ready to be aggressive in a cagey opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who operated with a tight guard to barely take the better stanzas.
The crowd's patience decreased because of frequent holding, with Parker falling to the floor several times during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Hatton Memorial Inspires Manchester Derby Battle
In the supporting bout, Arthur overcame Rea by divided decision in a excellent local rivalry contest to capture the European light-heavyweight belt.
The stadium fell silent for a extremely emotional homage ahead of the contest as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the first major televised boxing event in the location since the passing of Hatton. As the concluding sound disappeared, the silence became a roar of "there's only one Hatton".
The competition within the ring reflected the emotion. Arthur was knocked down by a significant blow flush on the chin in the early round, rising shakily to his footing on the count of eight.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was damaged early, significant bruising forming under his orbital area as the pair landed hard punches.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the pace hardly diminished over 12 rounds.
Arthur barely secured the decision with judges scorecards of even score, narrow lead and 115-112, but each competitor were persistent and courageous, all the qualities their hero the legend represented.
