Referee Marc Goddard stopped the 135-pound title fight at the 2:36 mark of the final round at Jeunesse Arena.
However, those instructions appeared to go in one ear and out the other as she continued to retreat and eat even more brutal leg kicks, which were slowly but surely restricting her movement.
"He should have listened to her at that moment", Nunes said.
"If she didn't have the right conditioning to fight then the coach should have thrown in the towel for sure". "I will stop fighting here because I think I reached the end". It's sad. Everyone must be saying a lot of bad things about him on social media, but I really think she needs to surround herself with people who want the best for her so she can really evolve for her next fights. "Unfortunately, tonight (the cornerman) failed", the Brazilian added.More news: Meghan Markle's Mom Arrives In London Ahead Of Royal Wedding
While Nunes maintained control for the majority of the second round, Pennington was finally able to drag the fight to the ground with about a minute to go, although she didn't do much with it except maintain the position before the fighters worked their way back to the feet a few seconds remaining.
"We tried to make that fight happen because it's a big fight and the fans wanted it, but it couldn't happen at the time so I moved on", she said, per Kevin Iole of Yahoo Sports.
And even after taking down the former Team Tate star, Nunes was met with more doggedness from Pennington, who was fast running out of ideas of how to dethrone the Brazilian.
Nunes had the clear advantage from the outset of the first round. "C'mon girl. I know it hurts, I know". She used to train with us. "It was the hardest fight in my career". Nunes said that when they leave, they'd all get a beer.More news: Rockets and Warriors-the one and two in the Western Conference
According to Fightmetric, Nunes outlanded Pennington in total strikes 152-79.
Despite offering very little in terms of offense, Pennington did keep the champion on her toes with some well-placed counter punches, though they had little effect on "The Lioness".
As for Pennington, she showed incredible toughness throughout the fight, although her corner didn't do her any favors by not stopping the contest when their athlete said she was done.
Having successfully defended her title three times now, Nunes is going to need a fresh face to compete against in her next outing.More news: Remembering 'Mr Wales', soldiers look forward to Harry and Meghan's big day
Nunes had Pennington backing up over the first two rounds, battering her lead leg to set up her boxing combinations.