Reigning Wimbledon champion Elena Rybakina clinched a spot in the second round of the Dubai Duty Free Tennis Championships by defeating another Grand Slam champion, Bianca Andreescu, 6-3, 6-4 on Monday.

Two more major champions, Jelena Ostapenko and Victoria Azarenka, joined 2020 Dubai runner-up Rybakina in the second round. Here are takeaways from the day:

First-strike tennis pays off for Rybakina: No.9 seed Rybakina held off 2019 US Open champion Andreescu in 1 hour and 32 minutes, using the power game that steered her to her 2022 Wimbledon title as well as this year's Australian Open final.

Read more: Swiatek, Rybakina among Laureus World Sports Award nominees

As usual, aces were key for Rybakina -- she had six. Additionally, Rybakina attacked Andreescu's second service, winning nearly 80 percent of those points to help her attain four service breaks.

Mental game clutch for the Kazakh: Rybakina's steeliness was just as important. Things could have been very different in the first set as Rybakina stared down two break points in the first game, but she erased those before breaking for 2-0 and holding that lead for the rest of the set.

In the second set, Rybakina pointed to her temple during a comeback from 3-1 down, as her well-executed groundstrokes wore down former World No.4 Andreescu's all-court guile.

"The second set, a few mistakes, a few good returns from Bianca, and I turned around and I was down," Rybakina said after her win. "But then I’m happy that I managed to win in two [sets].

"I think tactically I was playing great, just at a few moments, maybe I rushed a bit on the serve. [I lost] my serve two times, but then I’m happy that the return games I played really well."

Bouzkova awaits: Rybakina will take on World No.26 Marie Bouzkova in the second round. Bouzkova, a Wimbledon quarterfinalist last year, will play her second straight Grand Slam champion, after she beat 2020 Australian Open titlist Sofia Kenin in the first round on Sunday.

Rybakina goes into the match with a 3-0 head-to-head lead on Bouzkova, although Bouzkova pushed Rybakina to three sets for the first time in their most recent meeting, in Toronto last year.

Ostapenko, Azarenka join Rybakina in Round 2: Earlier on Monday, defending champion Jelena Ostapenko eased past Katarina Zavatska 6-1, 6-4 in 1 hour and 15 minutes.

No.13 seed Ostapenko had eight aces and won 80 percent of her first-service points in the match. Ostapenko will now meet Czech teenager Linda Fruhvirtova in the second round.

"[Zavatska is] not an easy opponent, I think," Ostapenko said. "I just today didn't give her many chances to play. I was playing more aggressive and took time away from her and made her play uncomfortable. I think that was the key."

Highlights: Ostapenko def. Zavatska | Azarenka def. Pavlyuchenkova

Additionally, No.15 seed Victoria Azarenka took out Anastasia Pavlyuchenkova 6-3, 7-5 in 1 hour and 50 minutes in their first-round match. Pavlyuchenkova was playing just her fourth event since returning from a seven-month injury break.

Pavlyuchenkova came back from 5-3 down to 5-5 in the second set, but former World No.1 Azarenka took the final two games to prevail. Azarenka will play Amanda Anisimova in the second round.

"Happy to win, for sure," Azarenka said. "I felt a bit too many ups and downs today. I didn't really feel that comfortable to lead and then kind of go back and try to restart. I know it's part of the game, it's part of tennis. But I just wanted to kind of close it out a bit earlier.

"Finding the way to win, it's also very good, especially when you're maybe not playing your best. But Nastia [Pavlyuchenkova] is a great player. I'm really happy to see her back."