British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight 10-round contest at the boxing arena.
But Parker had his moments, connecting with powerful clean blows in a fight where the styles didn't complement each other, with frequent clinching spoiling the action.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but how do champions respond? They succeed," the victor stated in the arena as he was met by disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-fight professional journey.
The Champion Secures Win in Dull Encounter
Buatsi's progress has stalled in recent times through management issues and extended periods of lack of fights.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - perhaps in what seems like a last chance - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who utilized a solid defense to barely take the more effective rounds.
The crowd's patience decreased during constant clinching, with Parker going down various instances during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a outstanding all-Manchester contest to win the European light heavyweight title.
The venue became quiet for a profoundly moving homage ahead of the contest as 10 bells tolled in memory of the city's native Hatton, who died 46 years old in September.
It was the first major televised boxing event in the city since the passing of Hatton. As the last bell faded, the stillness became a chant of "only one Hatton".
The action during the bout matched the feeling. The eventual winner was floored by a powerful punch flush on the jaw in the initial stage, rising shakily to his feet on the referee's count.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up early, noticeable damage appearing under his eye as the duo traded punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over the full distance.
Arthur edged the result with scoring tallies of even score, close margin and 115-112, but each competitor were persistent and full of heart, all the qualities their idol the legend stood for.
