Andy Murray made a disappointing start to his Wimbledon warm-up campaign on Tuesday, losing 6-3, 6-4 to Marcos Giron in the Stuttgart Open first round.
The former world No 1, a Stuttgart finalist two years ago, had spent time in Britain training on grass after his first-round Roland Garros defeat to Stan Wawrinka last month.
But that preparation did not pay off at the Weissenhof Club, whose courts are curated under guidance from All England Club experts.
Murray will hope to revive his grass game at Queen's Club, London, his final tune-up before what is almost certain to be the last Wimbledon of his career.
The 2013 and 2016 Wimbledon champion went down in 75 minutes, with Giron winning his first match here after a pair of first-round defeats.
The Scot will drop out of the top 120 in the world rankings as a result of his defeat.
In the opening set, Murray volleyed into the net from close range to trail 4-2 with Giron closing out the set three games later.
The 37-year-old won the first six points of the second set but was unable to keep up the momentum.
"I grew up watching Andy, it's an honour to be on the court with him," Giron, 30, said.
"I'm grateful to beat him and happy with the win. I was excited to get a grass lesson from him.
"It's unreal what he's done in his career, to play him on grass is unbelievable - I'm pumped with the win."
Jack Draper will line up as Giron's second-round opponent. The Briton beat the 54th-ranked American in the Australian Open first round in January over five sets.
Murray was beaten in the 2022 Stuttgart final by Matteo Berrettini, who advanced earlier 7-6 (10/8), 5-7, 7-5 over Roman Safiullin.