Tiafoe will be a big crowd favorite on Thursday in Key Biscayne. (AP)

Main-draw ATP action at the Miami Open started Wednesday, and with the tour lacking the well-defined hierarchy it's seen for so many years, this fortnight will give a plethora of young players the opportunity to step up on a big stage. 

Here are three first-round match-ups to see before the seeds join in for Round 2: 

1

Frances Tiafoe vs. Nicolas Kicker

Tiafoe won his first ATP title in Delray Beach just last month, but will look to put his first-round loss in Indian Wells behind him against the 25-year-old from Argentine. The 20-year-old American has made huge strides in his game, stringing together a slew of wins in Delray to put himself on the winner's podium. He has yet to taste ATP Masters 1000 success—though expect he will be a crowd favorite this week. 

2

Alex de Minaur vs. Yoshihito Nishioka

So far in 2018, Australian teenager de Minaur has been living up to his hype. He started the year in Brisbane by beating Steve Johnson and Milos Raonic. Then in Sydney, he backed that result up with a run to the final with wins against four Top 50 players. 

His 22-year-old opponent, Nishioka, sadly tore his ACL at the Miami Open in 2017. Returning for this season, he hasn't had any eye-popping results yet, but a win over De Minaur would definitely get the world's attention. 

 

First hit after knee surgery. Feeling no bad????

A post shared by Yoshihito Nishioka(西岡良仁) (@yoshihito0927) on

3

Stefanos Tsitsipas vs. Daniil Medvedev

Nineteen-year-old vlogger extraordinaire Tsitsipas' ranking hasn't quite caught up to the size of his game, but, as he plays more tournaments, it's getting closer. He's currently at a career-high No. 70. In his last match, in Indian Wells, he lost in the second round but managed to take a set off Dominic Thiem. 

Medvedev, slightly older and ranked slightly higher, recently recorded his first ATP title, the Sydney International, in which he defeated De Minaur in the final.