There is reason to believe that he will recover without difficulty, and he can take (and likely is taking) blood thinners to prevent another stroke. He is completely functional now and able to communicate with the press, constituents, his doctors, and his new colleagues in the Senate. Your repetition of the claim that his job performance will suffer is unfounded speculation.
It is of course not unfounded. You chose to downplay Fetterman's performance in the debate, saying it was high stress, but you cannot simply dismiss it.
But,
whether or not I am mistaken about how much of an impact Fetterman's language processing deficit will have in two months time (and
I can't be mistaken about it because I simply have no beliefs about it one way or another), it would still be true that the ability to process language is an important ability for a Senator to have.