Andy Murray said his grass game "needs to improve" if he is to make a decent Wimbledon showing after losing in the first round of the Stuttgart Open on Tuesday.
A two-time champion at the All England Club, Murray lost 6-3, 6-4 to star-struck American Marcos Giron, the number 54 who had not won a match in Stuttgart in two previous attempts.
"My game needs to improve, the level of tennis on the tour is high. I need to play better if I want to win more matches," Murray said.
The former world number one, 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.
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. The Scot will drop out of the Top 120 ranking as a result of his defeat but is not yet panicking with the July 1 Wimbledon start drawing near.
"I've had some tough months, but physically I feel OK just now - the ankle, the back. It's all felt better since going onto grass," he said.
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.
Murray, who only recently changed racquet brands, expressed disappointment over missing his Stuttgart chances.
"I've been struggling with breaking serve. I've not broken for a few matches and that's usually been a strength of mine.
"On a quick surface like grass, the sets are tight. When your chances come you have to be clinical - he was and I wasn't."
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.
Murray said his Paris Olympic future is yet to be decided.
"I still need to see what happens with the Olympics. I'm not sure of the doubles situation and don't know if it's worth playing only for singles.
"My body did not feel great on clay the last few months. I need to wait and see on that."