British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight 10-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective individual punches in a fight where the techniques never quite clicked, with excessive holding marring the contest.
The scoring judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," the victor commented in the ring as he was met by disapproval from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Various analysts believed Parker, thirty-one, should have been awarded the decision but the contender endured the second loss of his 28-bout professional journey.
Buatsi Earns Victory in Dull Affair
His career development has slowed in recent years through contract problems and extended periods of lack of fights.
Previously predicted as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under recent support.
He started carefully, with neither fighter ready to be aggressive in a cagey opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second appearance at light-heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who utilized a solid defense to narrowly win the cleaner periods.
The crowd's patience diminished because of constant clinching, with Parker falling to the floor various instances during close exchanges.
The underdog closed well, but several stanzas were hard to judge. However, former world champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Motivates Manchester Derby Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific all-Manchester contest to secure the European light-heavyweight championship.
The stadium fell silent for a profoundly moving homage before the fight as ten bells sounded in honor of the city's native Ricky Hatton, who died aged 46 in September.
It was the initial significant broadcast match card in the city since Hatton's death. As the last bell ended, the silence gave way to a shout of "there's just one Hatton".
The competition inside the ropes matched the sentiment. Arthur was sent to the canvas by a left hook directly to the chin in the second round, rising shakily to his footing on the eight count.
But the traditional red shorts of the fighter soon came forward again. On the opposite side, Rea - in competitive blue - was damaged soon, significant bruising developing under his face as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor barely secured the result with scoring tallies of 114-114, close margin and clearer margin, but both fighters were determined and courageous, exactly what their hero Hatton embodied.
