On Day 8 at the US Open, four matches were on tap in the women’s draw as players were forced to battle each other and the heat and humidity.

Bouchard Unable to Overcome the Heat and Makarova

Seventh-seeded Eugenie Bouchard, who advanced to at least the semifinals of the three previous Grand Slams this season, could not advance on Monday. She fell to Ekaterina Makarova 7-6(2) 6-4.

In the first set, 17th-seeded Makarova took advantage of 20 errors off the Canadian’s racket and attacked her second serve en route to a tiebreak win. The Russian dominated the tiebreak at 7-2. Makarova won 77 percent of her first serves during the set.

A frustrated Bouchard attempted to step up her attack early in the second set. However, Makarova continually caused damage with groundstroke winners down the line, and her deep, well-paced shots pressured the Canadian.

Later, following the fifth game of the set and on serve, a lethargic-looking Bouchard was treated during a medical timeout where staff appeared to attempt to cool down the 20-year-old with ice and fluids. In the extremely hot and humid New York day, it was an endurance test for a number of players on the courts, and many took advantage of 10-minute 'extreme heat' breaks between some sets. Bouchard may have hoped to have that opportunity at the end of the second set.

However, after returning to play, Bouchard quickly dug a hole on her serve and was unable to fight off three break points, falling to 2-4. Despite appearing out of sorts, she immediately broke back with the New York crowd behind her. But, clearly feeling the effects from the heat, Bouchard could not hold back Makarova, who broke serve once more and advanced to the quarterfinals.

Asked about her medical timeout, Bouchard responded, “Once in a while, I get a little bit light-headed. That's what happens.”

She also addressed the expectations to win. “I definitely felt a lot of outside expectations and pressure to win matches. I felt more like it's normal if I win and it's a bit more of a disaster when I lose,” she said. “But that's something that I need to block out.”

Serena Rolls to Quarters

Top seed Serena Williams found her serve on Monday and rolled to a two-set victory over Kaia Kanepi 6-3 6-3.

Williams, who has had moments where her serve has been erratic, found one of her better serving sets in some time. In the first set, Kanepi had no looks at a break point off the American's racket as Serena fired six aces in the set. Williams won all 16 of her first serves that were in play during the set.

In the second set, Williams continued to overpower the Estonian. Despite dropping her serve twice, she more than made up for her miscues with four breaks of service of her own. And after her inability to close out the match on her own serve, Williams broke Kanepi to advance.

Williams was pleased with her performance as she addressed the crowd. “I finally made a quarterfinal this year!” she said.

Azarenka Overcomes Feisty Qualifier

16th seed Victoria Azarenka continued her comeback against qualifier Aleksandra Krunic, who entered the match on the heels of wins against Petra Kvitova and Madison Keys. After an exciting and extremely competitive match, Azarenka advanced, 4-6 6-4 6-4.

For the first time since her run of success against U. S. Open seeds, Krunic showed some signs of nerves early, dropping the first three games. However, she quickly turned play around, gained some confidence, and surged past the two-time Grand Slam champion to a 5-4 lead. After a variety of tempo-changing shots, she broke Azarenka and took the opening set.

Early in the second set, the quickness and savvy of Krunic sent the crowd into a frenzy as she refused to allow her opponent to take the upper hand. However, in the seventh game of the set, the veteran finally found a chink in the Serb's service game, breaking through. She served out the set to even the match.

In the third set, as Azarenka's game settled down, perhaps Krunic's legs finally began to tire somewhat. It was the 21-year-old's seventh match in less than two weeks, having had to play qualifiers to enter the main draw.

However, just as it appeared the qualifier was on the ropes, at the crowd's urging, she broke back to even the set at 2-2. But midway through the set, the veteran found a break and despite a gallant effort from Krunic, Azarenka found a way to close out the match on her serve.

Pennetta Advances

11th seed Flavia Pennetta came into Monday's match hoping to duplicate last year’s U. S. Open run, when she advanced to the semifinals. She took one step closer by defeating Casey Delacqua 7-5, 6-2 in Arthur Ashe Stadium.

In the first set, neither player found her rhythm as both grappled with a multitude of errors and the inability to hold serve. But in a set that featured a combined 33 unforced errors and five breaks of service, Pennetta found enough winners to prevail.

In the second set, Pennetta cleaned up her game, while the 29th seed continued to struggle. The Italian took advantage, breaking twice while holding her serve throughout. She served out the set and the match to advance to the quarterfinals.