You keep saying the tactics made sense from the beginning, but CP was key to their win over city, and has been playing great. It was a terrible idea not to start him. And it was a terrible idea not to bring him on at half when down 3-1. And given the likelihood of getting a point here, it was extremely questionable to bring him on when Lampard did, given how important the final game is.
He's completely changed this game. He's without a doubt Chelsea's top player right now. Klopp had a look of approval after that banger.