British light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful single shots in a match where the styles never quite clicked, with frequent clinching spoiling the action.
The officials scored it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They prevail," the victor commented in the ring as he was greeted with disapproval from the spectators.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers thought the challenger, 31, merited the decision but the Derbyshire fighter experienced the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Encounter
His career development has stalled in recent years through promotional disputes and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter willing to be aggressive in a calculated initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to barely take the better stanzas.
The crowd's patience wore thin during frequent holding, with the challenger slipping to the canvas various instances during grappling.
Parker finished the stronger, but several stanzas were hard to judge. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Inspires Local Rivalry Fight
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a outstanding local rivalry fight to win the continental belt.
The stadium grew hushed for a extremely emotional memorial ahead of the contest as 10 bells tolled in remembrance of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the urban center since Hatton's passing. As the final chime ended, the stillness gave way to a shout of "only one Ricky Hatton".
The action during the bout matched the feeling. Arthur was knocked down by a significant blow flush on the face in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon came forward again. From the other corner, Rea - in rival City blue - was marked up soon, significant bruising forming under his face as the pair exchanged punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor barely secured the result with judges scorecards of even score, 115-113 and wider gap, but the two athletes were determined and full of heart, everything their idol the legend stood for.
