Top seed Medvedev crashes out at Wimbledon warm-up in Halle, Zverev through to semis
Medvedev lost 7-5, 7-6 (7-3) against the Spaniard. Eighth seed Bautista Agut now boasts a 5-2 career record against the 2021 US Open winner.
Medvedev, the former world number one, was runner-up on the Halle grass in 2022, losing to Poland's Hubert Hurkacz in straight sets in the final.
With a poor record on grass, Medvedev has never reached the quarter-finals at Wimbledon, missing last year's tournament due to a ban on Russian athletes due to the war in Ukraine.
In Friday's final match, third seed Andrey Rublev came from behind to defeat Dutchman Tallon Griekspoor, setting up a meeting with Bautista Agut.
Rublev lost the first set 3-6 but won the next two 6-3, 6-4, making it the second time he beat Griekspoor this season after another three-set win at the Qatar Open in Doha in February.
Olympic gold medallist Alexander Zverev also progressed into the semi-finals after defeating Chilean Nicolas Jarry.
The 26-year-old German, who made it to the semi-finals of this year's French Open, defeated Jarry in straight sets 7-5, 6-3.
"It's fantastic that I've been able to keep playing like I did in Paris, but there's still a few things to improve on" Zverev said.
Zverev will play in the semis for the third time. The German previously made it to the final of the Halle tournament in 2016 and 2017, losing to 10-time winner Roger Federer on both occasions.
Zverev will meet Kazakh Alexander Bublik in the last four after Bublik advanced when Italian fourth seed Jannik Sinner withdrew hurt in the second set of their quarter-final tie.
Bublik won the first set 7-5 and was up 2-0 in the second when Sinner pulled out with a right leg injury.
The Italian had taken a medical timeout at the end of the first set. He received treatment from a physiotherapist and played, and lost, two more games before pulling out.
Sinner, the 21-year-old world number nine, now faces a race against time to be fit for Wimbledon which starts in early July.