British light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a close 10-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling individual punches in a match where the techniques didn't complement each other, with frequent clinching disrupting the fight.
The officials had it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They prevail," the victor said in the arena as he was greeted with boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th career victory.
Several boxing experts felt Parker, 31, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-bout career.
Buatsi Earns Win in Dull Match
His career development has stalled in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers willing to be aggressive in a cagey early stages.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the middle rounds, the underdog had stayed in contention, causing problems for Buatsi, who utilized a protective stance to edge the more effective stanzas.
The audience's tolerance wore thin amid constant clinching, with the challenger going down multiple occasions during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. However, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Fight
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a excellent all-Manchester fight to secure the continental belt.
The stadium became quiet for a extremely emotional memorial ahead of the contest as 10 bells rang in honor of the city's native Hatton, who died at age 46 in September.
It was the premier televised match card in the city since the passing of Hatton. As the last bell faded, the stillness gave way to a shout of "only one Hatton".
The action inside the ropes reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the early round, rising shakily to his footing on the referee's count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was injured quickly, heavy swelling developing under his orbital area as the pair landed hard punches.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over 12 rounds.
The victor edged the result with scoring tallies of even score, 115-113 and 115-112, but each competitor were relentless and courageous, everything their hero the legend represented.
