In a match between two Grand Slam champions, Andreescu cooled off the in-form Garbiñe Muguruza, 3-6, 6-3, 6-2, in the pair's second career meeting, while Sorribes Tormo downed Ons Jabeur, 6-4, 0-6, 6-1 to continue her best-ever run at a WTA 1000 event.
"It was really tough. She started out playing really, really well. I don't think I was at the level I wanted to be right at the start of the match, because I knew she was going to come out really, really strong, and that's what she did," Andreescu told reporters after the match.
"But I had to re-adapt, which I did in the second set. I regrouped. I kept fighting. I changed my game plan a little bit as well. And it worked."
A set down and staring at a 15-40 deficit on serve at 1-1, Andreescu ripped off nine of the next 11 games to wrestle command of the match, and sealed victory in two hours and 11 minutes.
"I felt like at the beginning I wasn't as consistent. She was just playing really, really well, as well, on top of that," Andreescu continued.
"But I felt like I was going too much on her forehand in the first set, so I kind of regrouped and I tried to pick what I was doing right and what I was doing wrong. I just told myself, 'Okay, her backhand was still really good but I'll pick on that a little bit more.' That made a big difference."
Behind 34 winners and four breaks of serve, Andreescu snapped Muguruza's eight-match winning streak and earned a third consecutive win in Miami, her second time doing so in three tournaments played this season.
"I feel it was like a very tight match. I felt I had many opportunities," Muguruza said in defeat. "I had opportunities in the second set to take the lead. I just didn't convert them.
"So far, [it's] probably my best start of the year, and I'm happy about that. I take the positives. I know right now it is a tough moment, but in five minutes, I'm just going to change my mind and just look ahead to the clay court [season] which is my favorite surface. I'm happy with the way I'm playing."
Dating back to her breakthrough season in 2019, Andreescu is now 22-2 in her last five WTA 1000 events, and seeks to reach the semifinals in Miami for the first time when she faces the Spanish No.2 Sorribes Tormo.
"It's always satisfying getting that three-setter, especially after losing the first set. So to me what I was super happy about that match was how even when I'm down, and I knew this about myself," Andreescu said.
"Even when I'm down I know I can find a way. Most of the time, not all of the time. Most of the time, I can always find a way and come back and do really, really well.
"I keep proving that to myself, and it's really nice to get that under my belt. I felt super, super pumped the whole match, considering everything that's been happening. I'm just super, super happy."
After Andreescu took down the tour's leader in wins, improving her head-to-head against Muguruza to 2-0, she and Sorribes Tormo will play for the first time.
"I have seen her play. I know she gets to a lot of balls," Andreescu said. "She has a very heavy spinny ball. She's a crazy fighter. I want to go out there and fight even harder and hopefully I can do good things."