The ATP Washington event has had plenty of problems with rain this week and that may be the case on Thursday too so don't be surprised if this match is not in a position to take the courts.
Tiafoe's serve has improved, but he is still working on getting the best out of his return game although he may have a few more chances against the David Gofffin serve.
Goffin has not been the best form since the end of French Open, but he will be happy to be back on the hard courts and I think he will edge out Tiafoe in what could be a very fun match to watch once the rain clears away.