He has been recovering from a hamstring injury picked up in Bayern Munich's Champions League semi-final with Paris Saint Germain.
"Now that we have Alphonso back and healthy and ready to perform, I think it's a big moment for the team and a big boost for the team," Marsch said on Saturday.
Davies wanted to get on the pitch in Canada's final Group B game against Switzerland, which they lost 2-1, but Marsch told the 25-year-old it was too early.
"It was hard to watch those three games," said Davies. "It was painful. The only thing you want to do is play."
Marsch said protecting Davies was his aim. "You have to treat them (players) like they're Ferraris," he added.
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