British light heavyweight Buatsi secured a victory yet disappointing debut to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive 10-round fight at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a contest where the approaches failed to mesh, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi stated in the ringside as he was faced negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Various analysts believed the challenger, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
Buatsi Claims Victory in Dull Affair
The fighter's advancement has plateaued in recent years through contract problems and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He opened tentatively, with both competitors willing to take risks in a tentative early stages.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who operated with a solid defense to narrowly win the better stanzas.
The crowd's patience decreased during regular grabbing, with the challenger going down several times during clinches.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Fight
In the secondary fight, Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester battle to capture the European light-heavyweight belt.
The venue became quiet for a profoundly moving homage before the fight as a bell ceremony sounded in honor of local hero Ricky Hatton, who passed away aged 46 in last month.
It was the premier televised fight night in the urban center since Hatton's passing. As the last bell disappeared, the quiet gave way to a shout of "there's only one Hatton".
The fighting within the ring reflected the sentiment. Arthur was floored by a left hook squarely on the chin in the second round, getting up unsteadily to his feet on the eight count.
But the red-colored shorts of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was marked up early, significant bruising developing under his face as the duo exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity hardly diminished over the full distance.
The victor narrowly won the verdict with scoring tallies of 114-114, close margin and clearer margin, but the two athletes were relentless and courageous, exactly what their hero the legend represented.
