Caicedo wasn't only on a yellow - he was running on gas. He had a run up towards their box a couple of minutes before he was hooked, and he was visibly SPENT. Later it came out that he has been struggling with a sore back, too, but mostly he just seemed knackered. Leave him on and he either makes a mistake through exhaustion / arrives late at a tackle earning a second card / picks up an injury. To complain about Caicedo coming off is cheap after-timing.
As to who replaced him - that's more open to debate. I've always had some reservations about Lallana coming into a fast game as a sub. But equally, we were not looking after the ball at all, and he is the best player in our squad at doing so - so can see the logic. Alzate was the only other midfield option.
