The Dutchman, 20, was caught up in a big collision with around 50 kilometres remaining on the opening stage.
The fall reportedly caused him to sever a finger on his right hand, while Sebastian Henao (Team Ineos) also dropped out due to the crash.
Jumbo-Visma tweeted to say that the rider was in hospital being treated by a plastic surgeon. His condition was described as "fine".
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It was Leemreize’s first race as a professional after being promoted from the Jumbo-Visma development team last week.
The stage was won by Felix Grossschartner (Bora-Hansgrohe) as the fancied Alejandro Valverde (Movistar Team), Mikel Landa (Bahrain McLaren) and Remco Evenepoel (Deceuninck-Quickstep) finished in the top 10.
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