That's gutting news to lose both overseas batters to the SA test squad. We couldn't have expected SA to rest so many players, and call them both up for their debuts. I assume they will leave after the Gloucs away game on 20 June.
I suppose it could have been worse, because their first two weeks away coincidence with the return to Championship cricket (albeit Brevis was meant to play in those matches for us). But we're still looking at them missing potentially all of our final six Blast matches once the competition resumes again.
Fingers crossed for decent replacements.
(In theory either or both of them might return for our last one or two group games, because the test series will have finished by then. But those last two matches instead clash with SA's t20 matches - and given that they've been named in the test squad, one would assume they'll also be named in the t20 squad.)