Well, this is not ideal.
Boston draft pick out of Gonzaga Kelly Olynyk looked good in the Orlando Summer League, like the Celtics may have a piece that can be part of their future as they rebuild.
A lot of basketball players suffer from plantar fasciitis, which is an inflammation of the connective tissue that runs a long the bottom of the foot. It’s an overuse injury (which can be exacerbated by other factors such as shoe fit).
The only way to recover is really rest (there are other things that help, but you need rest). This is something that depending on the severity could be fine and not bother him during the regular season. But it’s something to watch.