We’re down to the semifinals at the Miami Open. What should we expect from two matches that could go either way?

Here’s a breakdown:

No.1 Ashleigh Barty versus No.5 Elina Svitolina

What to make of this one?

The head-to-head says Svitolina leads 4-1 in WTA tour-level matches, 5-1 when Fed Cup is included. But while Svitolina won those first five matches – including a fourth-rounder in Miami three years ago – Barty took the most recent. And it was a big one. The Australian came away from the 2019 Shiseido WTA Finals Shenzhen with a 6-4, 6-3 result over the defending champion.

How much weight does that carry?

“For sure the match in Shenzhen was extremely tough for me,” Svitolina said after beating Anastasija Sevastova to advance. “I hate losing finals, and especially Shenzhen Finals, it’s a huge event. I wanted to defend my title. So it was extremely tough for me to lose that one, and hopefully I can play better and get the revenge.

Rivalry Rewind: The Best from Barty vs. Svitolina in 2019

“I played her many times actually, even when she just was starting to play well. Now she’s No.1. She improved a lot for the past three, four years. She’s been playing extremely high level.”

Countered Barty, “Obviously against Svitolina we have had some exceptional battles in big tournaments. I think that test will be no different, another big match. She’s figured her way out through this draw very well.”

Svitolina has navigated her path quite nicely, most notably taking out No.9 seed Petra Kvitova in the fourth round.  At 26, Svitolina is two years older than Barty and into her first Miami semifinal, her first final four since winning Strasbourg last September. She’s a sprightly 13-5 on the year.

After sitting out for nearly a year because of the global pandemic, Barty has responded well in the first matches away from her home continent. She survived a match point against qualifier Kristina Kucova and needed three sets to get past three-time Miami champion Victoria Azarenka. By far her best effort was a 6-4, 6-7 (5), 6-3 quarterfinal victory on Tuesday over No.7 Aryna Sabalenka.

Barty is 12-2 in 2021 and might have felt some extra motivation with her top ranking on the line. But when No.2 Naomi Osaka fell to Maria Sakkari in Wednesday’s first quarterfinal, Barty will stay No.1 come Monday’s rankings.

“No,” Barty said emphatically when asked how much retaining the No.1 ranking weighed on her. “Not by any means. No, it’s an amazing thing to be No.1 in the world at the moment, but I promise you that’s not what makes me happy.

“Whether I’m No.1 or No.10 or I’m anything in between or whatever number it is, that number for me doesn’t determine if I’m a happy person or a happy tennis player. I come out here and I just work hard. I try and do the best that I can. I know that if I do that I sleep well at night and the sun comes up tomorrow.”

Tennis fans should hope these two reprise their monumental meeting two years ago at Indian Wells. Svitolina prevailed 7-6 (8), 5-7, 6-4 in a fourth-round match that required a numbing 3 hours, 12 minutes.

“It felt pretty long, because we had long rallies and long games,” Svitolina said after the match. “It actually felt longer than 3 hours, 12 minutes.”

Svitolina held two match points in the second set, but Barty leveled the match and actually led by a break in the third. The two players combined to create 38 break points and each converted six. Of the match’s 282 points, Barty won four more than Svitolina.

“Yeah, it was extremely high-intensity match,” Svitolina said. “Hopefully we can bring the same intensity for the semifinal, and I’m really looking forward to that.”

No.8 Bianca Andreescu vs. No.23 Maria Sakkari

Few people, perhaps even Sakkari, saw this coming.

Sakkari, the 25-year-old Greek, stunned No.2 Naomi Osaka 6-0, 6-4 – in a 69-minute quarterfinal. That was the end of the ninth-longest WTA win streak since 2000.

It may have been the biggest victory of Sakkari’s career, but it wasn’t a complete surprise. Inside the past two years, Sakkari has beaten nine Top 10 players: Serena Williams, Petra Kvitova and Elina Svitolina twice each, Sofia Kenin, Belinda Bencic, Aryna Sabalenka and Kiki Bertens. In fact, she is on a four-match win-streak against Top 5 opponents.

Read: How Maria Sakkari unleashed her power and rediscovered her identity in Miami

After saving six match points against Jessica Pegula in the fourth round, Sakkari exploded in the first set against Osaka, winning 26 of 34 points. She overcame a second-set break at 1-4 and later could be forgiven for losing focus in her on-court interview.

2021 Miami Highlights: How Sakkari snapped Osaka's streak for SF spot

“Sorry, I’m a little bit lost,” Sakkari said at one point. “I’m so excited. I’m super happy. I have no words. I’m speechless, yeah.”

She’s 12-4 for 2021, but will have to bring it down a few notches for her Thursday semifinal against Andreescu, whom she’s never played.

After losing the first three games to Sara Sorribes Tormo, Andreescu seemed destined to follow Osaka into the clay season. But the 20-year-old Canadian launched into hyper drive and won six of the set’s last seven games. It wasn’t easy, against Sorribes Tormo, but Andreescu prevailed 6-4, 3-6, 6-3 in 2 hours, 38 minutes.

After missing 18 months with a knee injury, there were questions about Andreescu’s health when she got off to a slow start to the year. She took a medical timeout in her third-round match against Amanda Anisimova, but survived in three sets, as she did in the fourth round against Garbine Muguruza.

Against Sorribes Tormo, a grinding, physical player who likes long rallies, Andreescu said she was tired but summoned enough energy to win.

“Yeah,” that girl can really run,” Andreescu said of Sorribes Tormo. “She played amazing tennis.”

Peter Staples/Miami Open

Against Sakkari, Andreescu will see a player who can be as athletic and aggressive as she is. The question: After three straight three-set matches, can Andreescu recover for her semifinal match in less than 24 hours?

Sakkari’s spirits couldn’t be higher after coming back to beat Pegula and, now, Osaka.

“Of course winning a match from six match points down gives you a lot of confidence,” Sakkari said. “I think also beating Serena was equally big, beating [Osaka] after 23 matches in a row without losing, it was a big thing, of course. Yeah, for sure it’s one of the biggest wins of my career.”

This one, to get to the most important final of her career, would be even bigger.