UK light-heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a match where the styles failed to mesh, with frequent clinching marring the contest.
Two judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest display but what do champions do? They prevail," Buatsi stated in the arena as he was met by boos from the audience.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Various analysts thought the challenger, thirty-one, deserved the win but the British boxer experienced the second loss of his 28-bout professional journey.
The Champion Claims Victory in Uneventful Encounter
Buatsi's progress has slowed in the past few years through management issues and long spells of inactivity.
Previously predicted as the future of UK boxing, he now stands trying to realize his potential - possibly in what seems like a last chance - under fresh management.
He began cautiously, with both competitors willing to take risks in a calculated early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who utilized a protective stance to barely take the more effective rounds.
The spectators' acceptance diminished during constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker closed well, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - working with the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to capture the European light-heavyweight belt.
The venue fell silent for a extremely emotional tribute before the fight as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the final chime ended, the stillness became a roar of "there's just one Hatton".
The competition within the ring matched the emotion. The eventual winner was knocked down by a powerful punch flush on the jaw in the initial stage, rising shakily to his footing on the eight count.
But the traditional red shorts of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up soon, heavy swelling developing under his orbital area as the duo landed powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur barely secured the result with judges scorecards of 114-114, 115-113 and clearer margin, but the two athletes were relentless and full of heart, all the qualities their idol the legend stood for.
