Canada's Bianca Andreescu has rallied to beat Garbine Muguruza of Spain 0-6, 7-6 (3), 6-1 in a clash of Grand Slam champions Sunday in the first round of the Adelaide International. (More Tennis News)

The 2019 US Open champion Andreescu trailed 0-6, 2-5 before staging a remarkable comeback to beat two-time major titlist Muguruza in 2 hours, 12 minutes. Andreescu improved her head-to-head record against former top-ranked Muguruza to 3-0.

“In the second set I really had to change my gameplan,” Andreescu said. “I told myself to go for it (and) whatever happens happens.

“I put more returns in the court, more serves in the court. I'm so glad I pulled that out. I have no idea how.”

Muguruza looked in outstanding form in the first set, hitting eight winners to two and converting three of five break points while not facing a break point herself.

Andreescu started the second set more strongly but Muguruza nailed a forehand winner to lead 4-2 and served for a 5-2 lead. Muguruza served for the match at 5-3 but Andreescu averted that danger and took a crucial 4-2 lead in the tiebreaker with a backhand down the line, before closing out the set with an ace.

Andreescu served well, then broke for 3-1 in the final set. She will now play either No.4 seed Veronika Kudermetova or Amanda Anisimova in the second round.

Top-ranked Novak Djokovic is expected to play his first round singles against Constant Lestienne of France on Monday. All eyes will be on Djokovic, who returns to Australia after being deported last year because of visa problems caused by his vaccination stance.

Djokovic won the Adelaide International as a 19-year-old in 2007 for his third ATP Tour title.

“I chose Adelaide because I wanted to get a tournament ahead of Australian Open,” Djokovic told reporters this week. “I wanted a normal 250 event.

“Judging by the list of players that are playing in a 250 event it's not really 250 event. It's maybe a 500 event or maybe a 1000. Some of the best players in the world playing here, both men and women's side.”

“The field is super strong. You have Medvedev, Felix, Rublev. You have really, really top guys. Also in the opening rounds you can play Thanasi Kokkinakis, who is title defender, right?”