The fourth-seeded Federer fought off two match points before beating No.10 seed Tomas Berdych 6-2 3-6 7-6 (8-6) in their quarter-final.
The fifth-seeded Spaniard and four-time runner-up only managed to break the Mahut serve once, but he did not face a break point in a relatively comfortable win. "I'm happy to come have through today", said Federer to ESPN after the match. While Zverev pushed Rafael Nadal to an epic five-set match at the 2017 Australian Open, Kyrgios has produced flashes of a future multi-time Grand Slam champion, albeit letting his emotions get the better of him on several occasions.
Kyrgios also hit 34 winners to 21, including a between-the-legs shot to win a point in the opening game of the second set.
Federer saved match points from 6-4 down in the decisive tie-break before holding on to triumph 6-2 3-6 7-6 (8/6) on a Czech double fault.
"It's a good start of the year, I think, for both of us", Nadal said.
Roger Federer vs Nick Kyrgios Miami Open 2017 semifinals is scheduled for 7 pm local time, 4.30 am IST, 11 pm GMT.
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But his lighter side was on show during a 6-4, 6-7 (9), 6-3 quarter-final win over Zverev, when he encouraged his fellow up-and-comer to challenge a call.
"It wasn't the big-serving match where you're only going to see so many looks, you know, so when you miss chances you always feel a bit frustrated sometimes".
Del Porto, ranked 32nd, appeared to lose pace and power after bandaging his wrist during the second set, yet he was able to prolong the contest by saving a break point in the seventh game before Federer's decisive forehand victor in the 10th. "He's going to continually make me better", said Kyrgios. Federer has been in blistering form, winning matches consistently, and the fourth seed will also hope to put up another magical performance in Miami. Kerber next meets 11th-seeded Venus Williams, who defeated seventh-seeded Svetlana Kuznetsova 6-3, 7-6 (4) in a matchup of former Miami Open champions.
Meanwhile, Rafael Nadal will square off against unseeded Italian Fabio Fognini in the other semi-final.
Federer was tested in the tie-break but came through to take the opener, his 13th straight set won against Bautista Agut. "I was trying to play my game and be aggressive".