Serena Williams completed the so-called Serena Slam and remained on course for a calendar Grand Slam in tennis after beating Garbine Muguruza in straight sets in the Wimbledon final Saturday. Perhaps focusing on the enormous achievements that lay before her, the 33-year-old had to battle her way through a shaky start and a nerve-ridden climax against an opponent who relished her first appearance on such a big stage. But Williams showed her champion’s mindset to get the job done and ultimately overwhelm her 21-year-old opponent, winning 6-4, 6-4 in an hour and 23 minutes to clinch her sixth Wimbledon crown.

The victory leaves Williams, who now has possession of all four Grand Slam titles, on a collision course with history at the U.S. Open in two months’ time. A triumph at Flushing Meadows would make her even with Steffi Graf for the most Grand Slam titles in the Open era, with 22, while it would also make her the first women since Graf in 1988 to make a clean sweep of the four major titles in tennis in a single year.

The gulf in experience between the two finalists going into the contest was startling. While Muguruza was playing in her first Grand Slam final, having never previously been beyond the elite eight before these past two weeks, Williams was competing in her 25th.

But there was little evidence of that disparity early on. Indeed, it was Williams who showed signs of nerves, serving three double faults to be broken in the very first game of the final. Meanwhile, Muguruza was striking the ball without fear, in sharp contrast to the first-time finalists in the past two years at the All England Club, Eugenie Bouchard and Sabine Lisicki. Unlike on those occasions, this was far from a damp squib of a final.

The fact that Muguruza, born in Venezuela to a Venezuelan mother and Spanish father, had experience in beating the American Williams surely helped in that regard. And a repeat of that stunning upset at last year’s French Open was certainly not beyond the bounds of reason given the start by both players.

But it was far too early to begin doubting a player of Williams’ incredible resolve. She has had to do things the hard way at this year’s Wimbledon -- coming back from the brink to beat home favorite Heather Watson before overcoming her sister Venus and great rival Victoria Azarenka. And, while her first-serve percentage remained below 50 percent throughout the first set, she began to find her timing and rhythm from the back of the court, exposing Muguruza’s deficiency in movement.

From 4-2 down, Williams reeled off four straight games with some deep hitting and the first signs of the pressure getting to her opponent. A double fault by Muguruza brought up set point, and Williams grabbed it emphatically with a perfectly hit crosscourt forehand.

Knowing that Williams was only liable to get stronger, while Muguruza had been playing at perhaps her highest level, the task facing the young tennis star at a set down was an enormous one. And predictably the match quickly started to drift away from the hard-hitting 2oth seed. Williams took 12 straight points through the middle of the second set to claim two breaks and move within sight of victory. But then came a dramatic and, for the neutrals, thrilling twist.

As the tension returned to Williams with the victory line in sight, Muguruza gave further demonstration that this is unlikely to be the last time she is seen on such a prominent stage, as she thrived on playing from behind. She retrieved both breaks of serve, the second after a sensational game that would have graced any final. But just as Muguruza was about to get back on serve, Williams retrieved her composure and came through to celebrate her sixth straight Wimbledon final with a break to love.