4 must-watch matches in the Australian Open Round of 16

The first week of the 2018 Australian Open is in the books, and after three rounds marked by extreme heat, marathon matches, wild comebacks, and American ineptitude, the men's and women's fields have been whittled down to 16 apiece.

While scads of high-seeded players got bounced in Week 1, the Round of 16 still offers up a bevy of enticing matchups. The Aussie Open isn't especially conducive to alternate-time-zone viewing, with matches running through the night. You'll be hard-pressed to catch every fourth-round match on the docket, but you can make sure to optimize the ones you do watch.

Here are four can't-miss matches in the Round of 16, which commences Saturday night for those of us in the Western Hemisphere:

Nick Kyrgios vs. Grigor Dimitrov

In perhaps the marquee match of the fourth round, these two gifted, flashy, oft-volatile players - who've been thriving in recent months with more restrained games and headier shot selection - will tangle for the third time in the last five months. Dimitrov got the better of Kyrgios in the Cincinnati final in August, and Kyrgios returned the favor with a tough three-set win in the Brisbane semis two weeks ago. This one is a toss-up.

Kyrgios was in fine form in the first week, and he's mostly done a good job of managing his emotions in pressure-packed moments in front of boisterous home crowds. He scored his first-ever win in Rod Laver Arena when he beat Jo-Wilfried Tsonga in the third round. Dimitrov struggled in his second-round win over qualifier Mackenzie McDonald (getting bageled in the fourth set before eking out an 8-6 fifth), but looked far better against Andrey Rublev in the third.

If both carry their most recent form over, expect a barn burner full of explosive forehands, cracking serves, emotional swings, and jaw-slackening shot-making. And with the winner set to play the victor of the unseeded Kyle Edmund-Adreas Seppi matchup for a spot in the semis, stakes don't come much higher.

Naomi Osaka vs. Simona Halep

Will Halep have anything left in the tank after her painful, near four-hour epic against Lauren Davis in the third round? If the world No. 1 feels any lingering effects, Osaka could make quick work of her.

The 20-year-old Japanese powerhouse has bashed her way to the fourth round without dropping a set, and was near-flawless in her third-round drubbing of top-ranked Aussie Ash Barty. Osaka has the kind of game that has given Halep the most trouble over the years: a punishing serve, an attacking mentality, and the ability to change the direction of nearly any ball with heavy, crunching groundstrokes. Halep has won both of their head-to-heads to date, but both went to three sets, and with nearly a year's worth of additional experience since their last meeting, Osaka could be ready to flip the script.

Halep's mental toughness has passed its first significant test at this tournament, and now we'll see how her physical toughness holds up. She managed to win the marathon over Davis on a wonky ankle, but Osaka has the firepower to hit through her in ways Davis could not. Will Halep take her second life and run with it, or will a first Slam title remain beyond her grasp? Whatever happens, we'll be treated to a classic contrast of styles in one of the most intriguing matchups women's tennis has to offer.

Madison Keys vs. Caroline Garcia

Has any player in Melbourne looked as convincing as Keys so far? The US Open runner-up has been frighteningly locked in, tearing through her first-week draw like tissue paper. She's won all six of her sets, doling out a bagel and two breadsticks along the way. She's been untouchable on serve, striking the ball with astonishing precision, and dictating nearly every exchange from the back of the court.

Garcia, though, represents an entirely different challenge. The eighth-seeded Frenchwoman has had her stumbles - needing three sets in each of her last two wins - and came into the tournament with questions surrounding her persistently sore back. But she's gotten better as the tournament has progressed, and showed in the fall what she's capable of when her body cooperates. Her smooth, agile all-court game should be a fun and potentially bamboozling counter to Keys' electric baselining.

Hyeon Chung vs. Novak Djokovic

Though on paper he may not pose as big a threat to Djokovic as Sascha Zverev would have, Chung could give the six-time champ a substantial challenge. Chung's third-round takedown of Zverev was a master class of patient, precision tennis, and if he can replicate that performance, he'll give Djokovic (and his precarious elbow) some problems.

Aside from a ghastly first set against Gael Monfils, that elbow has held up quite well so far, and Djokovic's serve hasn't seemed to suffer from his reworked motion. But he also hasn't been seriously pushed (except by the ridiculous heat that actually seemed to work to his advantage against Monfils), and he didn't need to be anywhere near his best to beat a less-than-stellar Albert Ramos-Vinolas in the third round.

In Chung, Djokovic will face a player not dissimilar from himself. The 21-year-old Korean is spry and athletic, defends extremely well to the backhand side, and can hit passing shots from compromised positions. Like Djokovic, his game is less about hunting for kill shots than putting his opponent in uncomfortable spots. Djokovic handily won the pair's only previous head-to-head, which came at this same tournament in 2016. Two years on, a more mature Chung and a more fragile Djokovic may produce a fascinating chess match.