Before Castillo can actually play for the Red Sox, he needs to have a completed work visa.
"And as soon as that's completed, which hopefully will be sooner rather than later, the sooner that happens, we would start to get him into games this season," said Cherington. "If it happens in time when the Minor League season is still going on, it may start with some Minor League games and then we'll see where we are. Our hope is that all these steps will be completed and we can see him in Major League games at some time in September."
The Minor League season ends on Sept. 1, but Triple-A Pawtucket is on track to make the playoffs, which could give Castillo some more time to get some action there before coming to the Red Sox.
Once Castillo is activated by the Red Sox, he is expected to start in center field.
Red Sox manager John Farrell got to spend some time with Castillo on Saturday.
Does Castillo remind Farrell of anyone in terms of body type?
"Oh gosh, I mean, he's obviously a very strong looking athlete," said Farrell. "Maybe a little bit shorter version of [Yasiel] Puig. You get a similar proportion to that type of body. What that means performance-wise, we'll see. We're confident in the athleticism and the overall strength."
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.