MIAMI, FL, USA -- 3rd-seeded Garbiñe Muguruza of Spain had a quick night at the office on Saturday, as the reigning Wimbledon champion swiftly eased past American Christina McHale, 6-2, 6-1, to advance to the Miami Open fourth round.

Muguruza was playing her first match of the event after her second-round opponent, 16-year-old American Amanda Anisimova, gave the Spaniard a walkover due to injury. But if Muguruza had any lingering rust due to a lack of match play, she did not show it against McHale, moving through in just 71 minutes.

The former World No.1 will now face another of last year's Grand Slam champions in the fourth round, as she will take on American Sloane Stephens. The reigning US Open champion moved past an injured Monica Niculescu just minutes before Muguruza won her match.

After each player held twice with minimal fuss, Muguruza cracked the set wide open at 2-2, as the Spaniard started to exhibit strong service returns, which would serve her well for the remainder of the match. After reaching break point, a powerful Muguruza backhand forced an error from the American, giving Muguruza a 3-2 lead.

Following an easy hold for 4-2, Muguruza again attacked McHale's serve with great zest. The American led in that game by 40-15,  but Muguruza continued to press, and ultimately won the final two points of the game with powerful returns which McHale could not get back into play, breaking again to lead 5-2.

The World No.3 was untroubled in her final service game of the set, closing it out 6-2 after 31 minutes. Muguruza won 65 percent of points on McHale's first serve, and was rarely tested on her own serve, fending off the single break point McHale had in the opening frame.

After Muguruza took an early 2-0 lead in the second set, McHale had to get through a marathon service game to try to keep her head above water. McHale watched five of her game points go begging and then saw Muguruza garner two break points. But Muguruza squandered those chances with unforced errors, and the steely American held for 1-2 after an 11-minute, seven-deuce game.

It seemed that McHale might take heart from that exceptional effort, and she reached break point in the next game, hoping to level the set. But McHale lost that opportunity after a forehand miscue, and Muguruza eventually held for 3-1 with a winning volley.

That would be the start of an 11-point run for the Wimbledon champion, as she broke McHale at love for 4-1 and held at love for 5-1. McHale had a game point to hold for 5-2, but big hitting off the backhand wing by Muguruza won her two consecutive points, setting up match point. A final forehand unforced error by McHale sent Muguruza skipping into the round of 16.

More to follow...