British light-heavyweight Buatsi earned a win yet unimpressive beginning to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a competitive 10-round bout at the Manchester venue.
But the challenger found success, landing some telling single shots in a fight where the techniques never quite clicked, with frequent clinching marring the contest.
Two judges scored it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest display but what defines champions? They prevail," Buatsi stated in the ringside as he was met by disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, merited the win but the contender experienced the second setback of his 28-fight professional journey.
The Champion Claims Win in Slow Match
Buatsi's progress has slowed in recent years through promotional disputes and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a last chance - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a tentative initial rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who worked behind a solid defense to narrowly win the more effective rounds.
The crowd's patience diminished amid constant clinching, with the challenger falling to the floor several times during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Fuels Local Rivalry Fight
In the secondary fight, Arthur beat Rea by close verdict in a excellent all-Manchester fight to win the European light-heavyweight title.
The stadium became quiet for a extremely emotional homage ahead of the contest as 10 bells sounded in memory of Manchester's own Hatton, who died at age 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the last bell ended, the quiet transitioned to a chant of "only one Ricky Hatton".
The fighting during the bout equaled the emotion. The eventual winner was floored by a significant blow directly to the face in the second round, getting up unsteadily to his position on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling forming under his face as the duo landed powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the decision with official scores of even score, close margin and 115-112, but the two athletes were persistent and full of heart, exactly what their idol the legend represented.
