Top-seeded Daniil Medvedev's 12 aces weren't enough as the Australian Open runner-up was beaten 7-6 (4), 6-4 by Dusan Lajovic in the first round of the ABN AMRO World Tennis Tournament on Wednesday.

It wasn't the day's only upset in Rotterdam, with third-seeded Alexander Zverev also losing.

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Russia's Daniil Medvedev breaks his racket in the first round men's singles match of the ABN AMRO world tennis tournament against Serbia's Dusan Lajovic at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Top-seeded Daniil Medvedev's 12 aces weren't enough as the Australian Open runner-up was beaten 7-6 (4), 6-4 by Dusan Lajovic in the first round of the ABN AMRO World Tennis Tournament on Wednesday.

Russia's Daniil Medvedev reacts after missing a shot against Serbia's Dusan Lajovic in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

“I think I was very focused the whole match," Lajovic said. “This was the key today, not to make the little mistakes.”

Serbia's Dusan Lajovic plays a shot against Russia's Daniil Medvedev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Sixth-seeded David Goffin needed just over an hour to beat Jan-Lennard Struff 6-4, 6-0. He'll meet qualifier Jeremy Chardy in the second round.

Germany's Alexander Zverev plays a shot against Kazakhstan's Alexander Bublik in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Germany's Alexander Zverev plays a shot against Kazakhstan's Alexander Bublik in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Kazakhstan's Alexander Bublik plays a shot against Germany's Alexander Zverev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Kazakhstan's Alexander Bublik plays a shot against Germany's Alexander Zverev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Medvedev had 25 unforced errors against Lajovic's 12, along with eight double faults, and he broke his racket in frustration. The third-ranked Russian last played Feb. 21 in his straight-sets loss to Novak Djokovic in the Australian Open final.

Russia's Daniil Medvedev breaks his racket in the first round men's singles match of the ABN AMRO world tennis tournament against Serbia's Dusan Lajovic at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Russia's Daniil Medvedev breaks his racket in the first round men's singles match of the ABN AMRO world tennis tournament against Serbia's Dusan Lajovic at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

“I think I was very focused the whole match," Lajovic said. “This was the key today, not to make the little mistakes.”

The 30-year-old Serbian player faces Borna Coric of Croatia in the second round.

Alexander Bublik beat Zverev 7-5, 6-3 to set up a second-round meeting with Tommy Paul. Zverev, coming off a quarterfinal loss to Djokovic in Australia, went a break up in each set against Bublik but each time was then broken twice himself.

Russia's Daniil Medvedev reacts after missing a shot against Serbia's Dusan Lajovic in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Russia's Daniil Medvedev reacts after missing a shot against Serbia's Dusan Lajovic in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Sixth-seeded David Goffin needed just over an hour to beat Jan-Lennard Struff 6-4, 6-0. He'll meet qualifier Jeremy Chardy in the second round.

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Serbia's Dusan Lajovic plays a shot against Russia's Daniil Medvedev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Serbia's Dusan Lajovic plays a shot against Russia's Daniil Medvedev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Germany's Alexander Zverev plays a shot against Kazakhstan's Alexander Bublik in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Germany's Alexander Zverev plays a shot against Kazakhstan's Alexander Bublik in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Kazakhstan's Alexander Bublik plays a shot against Germany's Alexander Zverev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)

Kazakhstan's Alexander Bublik plays a shot against Germany's Alexander Zverev in their first round men's singles match of the ABN AMRO world tennis tournament at Ahoy Arena in Rotterdam, Netherlands, Wednesday, March 3, 2021. (AP PhotoPeter Dejong)