Poch is not known for rebuilding and Chelsea needs someone that can manage potential.
i don't think Pochettino can lead Chelsea to trophies, they will definitely bounce back to become a decent team, but they aren't going to compete for the EPL title as some people think, their goal next season should be to get themselves back into the CL and prolly win either the Carabao or FA Cup.
That should be their goal for next season, to start building their team before they start aiming for the premier league title. With the kind of quality players Chelsea has(although some players will be sold off, and bought also) If Pochettino can be able to utilize them well, the Chelsea club will be formidable by next season. This will take time anyway to come by