The Belgian crashed prior to the start of the race on June 9 while training in the Ardennes, and had injuries to the right side of his body, including a hematoma on his hip.
Over the course of the race, he was not able to keep a good position on the bike and developed pain in his knee. After abandoning the race, he returned to Belgium where he underwent testing at a Herentals clinic, and had fluid drained from his hip. He now will take several days rest before resuming his training schedule.
"It's a shame, especially because I am sad I can't be there to help Tony Martin defend his leader's jersey at Tour de Suisse," Boonen said. "He has been a real fighter and has also helped his teammates when they've had opportunities. I wish I could help return the favor in the last days. But, I think it's a wise decision to stop now and recover. I couldn't continue like this, the pain was becoming more intense day-by-day. I wish to the team, and Tony, all the best for the end of Tour de Suisse."
Boonen's next goal is the Belgian championships on June 29, where he will seek to regain the title from last year's winner Stijn Devolder.