British light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive ten-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a contest where the styles didn't complement each other, with frequent clinching spoiling the action.
The officials had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They prevail," Buatsi commented in the arena as he was faced boos from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, merited the decision but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
His career development has slowed in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what seems like a last chance - under new promotional backing.
He began cautiously, with neither fighter willing to take risks in a tentative early stages.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the cleaner stanzas.
The spectators' acceptance wore thin because of constant clinching, with the challenger falling to the floor several times during close exchanges.
The underdog finished the stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the likes of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a terrific local rivalry contest to secure the European light heavyweight belt.
The stadium grew hushed for a extremely emotional memorial ahead of the contest as a bell ceremony rang in memory of local hero Hatton, who died aged 46 in September.
It was the first major televised match card in the location since Hatton's passing. As the concluding sound faded, the stillness gave way to a roar of "only one Hatton".
The action inside the ropes equaled the feeling. The eventual winner was sent to the canvas by a left hook directly to the chin in the initial stage, standing uncertainly to his position on the referee's count.
But the traditional red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was damaged quickly, significant bruising appearing under his face as the pair traded hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the result with scoring tallies of draw, narrow lead and clearer margin, but each competitor were determined and courageous, everything their idol Hatton stood for.
Lena Hofmann ist eine erfahrene Journalistin mit Schwerpunkt auf gesellschaftlichen Entwicklungen und kulturellen Ereignissen in Europa.