British light heavyweight Buatsi made a winning yet disappointing beginning to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a tight ten-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a contest where the approaches never quite clicked, with frequent clinching spoiling the contest.
Two judges had it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi said in the ringside as he was greeted with negative reactions from the crowd.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts thought the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-match career.
Buatsi Secures Victory in Dull Affair
His career development has stalled in recent times through contract problems and considerable time of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to achieve expectations - possibly in what seems like a last chance - under fresh management.
He began cautiously, with the two boxers willing to be aggressive in a calculated initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second fight at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who worked behind a tight guard to barely take the cleaner stanzas.
The spectators' acceptance wore thin because of constant clinching, with the challenger going down multiple occasions during grappling.
Parker finished the stronger, but many rounds were hard to judge. However, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a excellent local rivalry contest to capture the continental title.
The stadium grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony rang in honor of the city's native Hatton, who died at age 46 in September.
It was the first major televised fight night in the city since the passing of Hatton. As the final chime disappeared, the stillness became a roar of "there's only one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the chin in the early round, getting up unsteadily to his footing on the count of eight.
But the red-colored attire of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was marked up early, significant bruising forming under his orbital area as the pair exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the intensity hardly diminished over 12 rounds.
Arthur barely secured the decision with judges scorecards of even score, close margin and 115-112, but the two athletes were persistent and courageous, exactly what their idol Hatton embodied.
