Starting the next season with a couple of losses would be the worst ever, but I don't know whether the pressure on Pochettino would even be that high then. He would exactly sell bad news to the media like you said it. He would say that cleaning up the mess will take some time whereas if they are successful he will say how brilliantly they prepared for the season. But I think that he is in quite a relaxed position and Chelsea wouldn't sack him early on in the season because what would they do then? Get another Potter? That's the advantage as a coach when you start from nothing.
Right now they need to have done their homework about players selection because this is first thing which needs good intention, and they are doing positive with first player is already arrived from RB Leipzig hopefully in coming days we will have few more quality players with the help of these new and few old things could be improved and after this hopefully they will go ahead with some friendly matches which will give them better idea which players are going to have better performance and if this all gone as plan than surely their start could be ideal, and we will have good performance from them throughout season.
But on other-side if we have no ideal start like we are looking then surely things will take time and then after few rounds they will be able to adjusted and give their best as requirements which is not problem because in coming season they will be play only in Premier League and few domestic cups which are not problem for them.