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The three-time major champion fell at the first hurdle for the seventh time this season, with Giron prevailing 6-3 6-4 after 75 minutes in Stuttgart.

Giron, runner-up to compatriot Tommy Paul in Dallas in February, broke in game six as he won nine out of 10 points, before going on to take the opening set.

Murray - a Stuttgart finalist in 2022 - looked to respond as he won eight of the opening nine points at the start of the second.

However, he saw two break points go begging as Giron held before breaking to 15 in game three.

It proved decisive for the American, who clinched victory with a love hold to set up a last-16 clash with Jack Draper.

Giron hit seven aces and won 80 per cent (33 out of 41) of his first-serve points on the way to claiming his first ATP win over a current or former world number one.

The 999th singles match of Murray's career ended in an 11th defeat of 2024. Having not won a completed match since beating Tomas Etcheverry at the Miami Open, the 37-year-old will drop out of the world's top 100 next week for the first time since January 2022.