British light heavyweight Buatsi earned a win yet disappointing start to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a competitive 10-round fight at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a contest where the approaches never quite clicked, with constant grabbing marring the fight.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what do champions do? They win," the victor stated in the arena as he was met by negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts felt the challenger, thirty-one, deserved the decision but the Derbyshire fighter endured the second loss of his 28-match professional journey.
The Champion Claims Win in Slow Encounter
His career development has stalled in recent years through contract problems and considerable time of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers prepared to take risks in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the better stanzas.
The audience's tolerance decreased because of frequent holding, with Parker falling to the floor multiple occasions during grappling.
The underdog ended stronger, but several stanzas were hard to judge. However, former world champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Homage Motivates All-Manchester Contest
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a terrific Manchester vs Manchester fight to win the European light heavyweight belt.
The venue became quiet for a profoundly moving tribute prior to the bout as 10 bells rang in remembrance of the city's native Hatton, who passed away 46 years old in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound faded, the silence gave way to a chant of "only one Ricky Hatton".
The fighting within the ring matched the feeling. The eventual winner was floored by a significant blow squarely on the jaw in the early round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was marked up early, heavy swelling forming under his orbital area as the duo exchanged punishing blows.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur edged the decision with scoring tallies of 114-114, narrow lead and 115-112, but each competitor were persistent and courageous, all the qualities their hero the legend represented.
