It’s baffling they wanted Sargent initially to play Darrin. If he had, I think the series would’ve only lasted a year. It’s not that Sargent was a bad actor, merely miscast here. He was actually fine if he played a single man or even a widower.
I read that by the time Sargent was brought on board, the show was actually so out of ideas that it was remaking old episodes with Sargent instead of York, so it sounded like the show in general was out of gas by that point anyway.