In the round of 16, she will face her compatriot Wang Qiang. The 18th-seeded Wang Qiang moved into the fourth round after No 10 seed and eight-time Miami champion Serena Williams had to withdraw prior to their scheduled match, due to a left knee injury.

Wang went up a break early in the first set at 2-1, but Collins' aggressive hitting and sturdy defense helped her break back twice for a 4-2 lead.

Wang, who won her first WTA title in the Mexico Open earlier this month, stepped up her game just in time and broke Collins' serve in the 7th and 11th games to take the first blood.

Wang won 80 percent of first-serve points in the set, while Collins' 16 winners were undone by her 22 unforced errors.

Collins did well and hold serve in the first game of the second set, but Wang stayed calm and started to take control. The Chinese player broke through in a tense game to claim a 2-1 lead, and extended that advantage further with a second break to go ahead 4-1 after a clutch of errors from Collins.

After that, Wang was never troubled en route to her victory.