British light heavyweight Buatsi secured a victory yet disappointing beginning to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close ten-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a fight where the techniques never quite clicked, with frequent clinching spoiling the fight.
The scoring judges had it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but how do champions respond? They prevail," the victor said in the ring as he was faced negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the victory but the British boxer endured the second defeat of his 28-bout professional journey.
Buatsi Earns Victory in Slow Affair
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a last chance - under recent support.
He opened tentatively, with both competitors willing to overcommit in a cagey early stages.
Parker, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who utilized a tight guard to narrowly win the better stanzas.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor various instances during close exchanges.
The underdog closed well, but many rounds were challenging to assess. However, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a terrific all-Manchester battle to win the European light heavyweight belt.
The venue became quiet for a deeply poignant homage ahead of the contest as 10 bells sounded in honor of local hero Ricky Hatton, who succumbed 46 years old in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the final chime ended, the stillness gave way to a shout of "only one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was knocked down by a left hook squarely on the chin in the initial stage, rising shakily to his position on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was damaged soon, heavy swelling appearing under his face as the pair landed hard punches.
Rea, 27, landed power punches but the champion, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
Arthur barely secured the verdict with official scores of 114-114, narrow lead and clearer margin, but the two athletes were determined and full of heart, exactly what their inspiration the legend represented.
