"I thought it was a little derogatory toward women," she told Lucca during her critique.
Sure, the song choice had been that of Lucca's coach Adam Levine, but Lucca fully supported the suggestion.
"I'm not going to let one person bring me down," he told PEOPLE after the show. "Clearly that seems like part of her strategy."
Having thrown multiple negative comments in his direction, including calling him "one-dimensional," Aguilera has left her former fellow Mouseketeer wondering: "Did something happen that I don't remember?"
Lucca says he's even asked mutual pals for clues about Aguilera's behavior.
"I have had conversations with old friends [from The Mickey Mouse Club] and I'll ask, 'Is there something I missed?' " he says. "I just don't know."
But, adds Lucca, "She definitely seemed to turn the corner when Justin Timberlake Tweeted [his support for me]. That gave me the indication that maybe it had something to do with their relationship."
Lucca, who says the drama may actually be helping him win votes, also wonders if her criticism has something to do with a rivalry among The Voice's celebrity coaches.
"It seems like a her-and-Adam thing. It's too bad because out of the four of them I think she may be the most knowledgeable about singing and the business. But she gets in her own way. Its a lack of self awareness or something."
When asked about the feud post-show, Team Cee Lo's Juliet Simms said, "I have nothing but good things to say about Christina. She is entitled to her opinion."
Meanwhile Chris Mann, of Team Christina, said he felt protective of his coach and wasn't happy with the way Lucca handled things.
"I thought it was uncomfortable," said Mann. "You are calling her a b––. I felt defensive as a guy with the only female coach. But I thought Christina handled it well and it was funny that Adam had a 'Team Xtina' shirt on."
The winner of The Voice – either Lucca, Simms, Mann or Blake Shelton's Jermaine Paul – will be announced on Tuesday's two-hour finale (9 p.m. ET) on NBC.