Gervonta "Tank" Davis was paying close attention when champ Teofimo Lopez lost his belts and undefeated record last weekend ... telling TMZ Sports he learned a valuable lesson, don't underestimate your opponent!
"Just a mistake he made," Davis says, "Going in there thinking someone's a slouch."
Tank added ... "That just taught me to never go in there thinking I won already and I didn't."
Of course, 24-year-old Lopez, the former unified lightweight champ, lost to George Kambosos Jr. last weekend ... in what was a major upset.
It was Teofimo's first fight since he was on the other side of a shocking upset ... when he beat Vasiliy Lomachenko in October 2020.
Back to 27-year-old Davis -- who is a perfect 25-0 (24 KO) in the ring -- a record he'll put to the test when he steps in the squared circle with 23-year-old Mexican boxer Isaac Cruz this Sunday on Showtime PPV.
"I'm looking toward going in there and putting on a show. It's the biggest fight of my career," Tank says.
"Just be ready. I'm ready. Give the fans what they want to see."
Tank's last match was back in June ... when he defeated Mario Barrios, becoming the WBA regular lightweight champion after moving up in weight class.
Davis also addressed Kambosos ... who told us he was the best lightweight fighter in the world this week -- a sentiment with which Tank doesn't agree.
"He's supposed to feel like that. I mean, he just won," the Baltimore native says. "Maybe he was in the heat of the moment."
"But, there's a lot of lightweights to show him that he's not the best."
Davis will try and prove he's better this Sunday 💪