UPDATE: Serena Williams withdrew from the tournament on Sunday citing inflammation in her shoulder, leading to a reshuffling of the draw that caused the following shifts:

– Halep has been drawn into the bottom half of the draw, along with No.2 Angelique Kerber, and No.8 Roberta Vinci, and No.10 Svetlana Kuznetsova. Before Serena’s withdrawal she had a tricky road to the final, but with No.3 Garbiñe Muguruza now moving up to replace Serena in the top half of the draw, Halep’s path is slightly easier. She opens up against either Daria Gavrilova or Annika Beck, with a potential third round match against Karolina Pliskova. Her projected quarterfinal opponent could be either Kuznetsova or Petra Kvitova.

– Muguruza replaced Serena on the top line of the draw and will open against either Monica Puig or a qualifier. She could play Stanford finalist Johanna Konta in the third round with either Dominika Cibulkova or Carla Suárez Navarro looming in the quarterfinals. If the draw holds to form, she could see Venus Williams, Agnieszka Radwanska, or Madison Keys in the semifinals.

Can Simona Halep match her 2015 summer season?

This time last year Simona Halep was down in the dumps. She was still smarting from two bad early losses at the French Open and Wimbledon, and in her mind her season was over. That mentality freed her up to play some of her best tennis of the season, making the final in Toronto, final in Cincinnati, and her first-ever semifinal at the US Open.

Now she has to defend it.

So can Halep, currently ranked No.5, replicate or better that run? One thing is for sure: her decision to skip the Olympics can only help. The Romanian star announced last week that she would opt out of Rio due to concerns over the Zika virus. While missing the Olympics will be disappointing, the decision does free Halep up to focus on a real shot at winning the US Open. In fact with the bulk of the players interrupting their season by heading down to the Olympics, she could be the who takes advantage of an unfocused, fatigued, depleted field this summer.

Can Garbiñe Muguruza get back on track?

It took a month and a half before Angelique Kerber came down from the high of winning her first major title at the Australian Open. But by the end of March she was back to playing high-quality tennis and imposing herself in the draws. Since winning the French Open, Muguruza has gone 1-2, losing to Kirsten Flipkens in Mallorca and Jana Cepelova at Wimbledon. Again, a dip is expected earning your first major title, but when will it turn around for Muguruza?

The summer offers a big opportunity for the young Spaniard. She floundered here last year – again, after making her first Slam final at Wimbledon – winning just one match through the entire Emirates Airlines US Open Series (including the US Open). That opens up a big point grab for her this year, where she can gain some ground on Kerber and Serena in the rankings.

Can Angelique Kerber play healthy?

The World No.2 withdrew from Bastad last week due to an elbow injury and is now in a tough situation of balancing her need to play with her need to rest, especially with the upcoming Olympics.

Can Venus Williams ride that momentum?

Could we see Venus in Singapore for the BNP WTA Finals Singapore presented by SC Global? She’s currently 18th in the Road to Singapore rankings but she could make a big move if she continues her current form. After making the fourth round of the French Open and the Wimbledon semifinals, she’s into the semifinals of the Bank of the West Classic this weekend. She looks relaxed and calm on court, and when she’s needed it she’s been able to elevate her game to get some tough wins. Another deep run in Montréal could really boost her chances not only to qualify for Singapore but also get her back in the Top 5.

First Round Matches to Watch: Lucie Safarova vs. Eugenie Bouchard, Monica Niculescu vs. Jelena Ostapenko, Yulia Putintseva vs. Anastasia Pavlyuchenkova, Madison Keys vs. Elena Vesnina, Caroline Garcia vs. Barbora Strycova, Alizé Cornet vs. Andrea Petkovic, Misaki Doi vs. Daria Kasatkina.

All photos courtesy of Getty Images.