UK light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, landing some telling single shots in a contest where the styles didn't complement each other, with constant grabbing spoiling the action.
The officials had it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest performance but what defines champions? They succeed," Buatsi stated in the ringside as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Various analysts thought the challenger, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
The Champion Secures Victory in Uneventful Match
The fighter's advancement has stalled in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of British boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors willing to be aggressive in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was making just his second fight at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a solid defense to barely take the more effective stanzas.
The crowd's patience diminished amid frequent holding, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor advances, but with the presence of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Hatton Memorial Motivates Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester contest to win the European light-heavyweight belt.
The arena became quiet for a deeply poignant tribute prior to the bout as ten bells sounded in honor of the city's native Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised fight night in the urban center since Hatton's death. As the last bell ended, the stillness became a shout of "only one Hatton".
The action within the ring equaled the emotion. The eventual winner was knocked down by a significant blow flush on the chin in the second round, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged soon, heavy swelling forming under his eye as the fighters landed hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur barely secured the result with official scores of 114-114, 115-113 and clearer margin, but each competitor were relentless and courageous, all the qualities their inspiration Hatton embodied.
