UK light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, landing some telling individual punches in a match where the approaches failed to mesh, with frequent clinching spoiling the action.
Two judges had it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," Buatsi commented in the arena as he was faced disapproval from the crowd.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Some ringside observers believed the challenger, thirty-one, merited the decision but the Derbyshire fighter endured the second loss of his 28-fight professional journey.
Buatsi Claims Win in Slow Match
His career development has stalled in the past few years through management issues and extended periods of lack of fights.
Once tipped as the rising talent of the British fight scene, he now stands trying to realize his potential - possibly in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who operated with a protective stance to edge the more effective rounds.
The crowd's patience diminished during frequent holding, with the challenger falling to the floor several times during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Battle
In the supporting bout, Arthur defeated Rea by close verdict in a excellent all-Manchester battle to win the European light heavyweight championship.
The arena became quiet for a extremely emotional tribute prior to the bout as a bell ceremony tolled in honor of the city's native Ricky Hatton, who died aged 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the final chime ended, the stillness gave way to a roar of "there's only one Ricky Hatton".
The fighting during the bout matched the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the red-colored shorts of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was damaged soon, noticeable damage appearing under his orbital area as the duo landed hard punches.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with powerful upward punches as the action hardly diminished over 12 rounds.
The victor edged the verdict with judges scorecards of draw, narrow lead and clearer margin, but the two athletes were persistent and courageous, exactly what their idol the legend represented.
