UK light heavyweight Buatsi made a winning yet disappointing debut to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close 10-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling clean blows in a match where the styles didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 to the winner, with the third a even score.
"It wasn't my greatest performance but how do champions respond? They prevail," Buatsi commented in the ringside as he was greeted with boos from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts thought the challenger, 31, should have been awarded the win but the Derbyshire fighter endured the second setback of his 28-match professional journey.
Buatsi Claims Victory in Slow Match
His career development has stalled in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a last chance - under fresh management.
He began cautiously, with the two boxers prepared to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second appearance at light heavyweight.
By the halfway stage, Parker had kept it close, causing problems for Buatsi, who worked behind a tight guard to edge the better stanzas.
The audience's tolerance diminished because of regular grabbing, with Parker going down multiple occasions during grappling.
The underdog finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the supporting bout, Arthur defeated Rea by divided decision in a outstanding local rivalry battle to secure the European light-heavyweight championship.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as 10 bells sounded in remembrance of Manchester's own Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the last bell disappeared, the silence transitioned to a roar of "only one Ricky Hatton".
The competition within the ring matched the sentiment. Arthur was floored by a significant blow directly to the jaw in the early round, getting up unsteadily to his position on the eight count.
But the red-colored equipment of Arthur soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up soon, significant bruising appearing under his face as the duo traded hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
The victor barely secured the verdict with official scores of draw, 115-113 and 115-112, but each competitor were persistent and brave, everything their idol Hatton represented.
