Rosenior made nine changes from the side that beat Aston Villa 4-1 earlier in the week, leaving Cole Palmer, Moises Caicedo and Enzo Fernandez out of the squad.

The hosts led through Sam Smith before an own goal from Arthur Okonkwo levelled the score. Callum Doyle restored Wrexham's lead late on, but Josh Acheampong equalised to force extra time.

The game swung when George Dobson was sent off after a VAR review upgraded his yellow card for a challenge on Alejandro Garnacho. Garnacho and Joao Pedro then scored in extra time to seal the win.

"We're through. It wasn't the best performance. A really, really difficult game," Rosenior said.

"You have to give your players opportunities. You have to see your squad and manage your squad. This team played the most games than any other club over the last 18 months in world football. It's crazy to just keep going and risk player injuries when we want to achieve what we want to achieve.

"Some of the elements of our play was very good, and we are through to the next round."

Asked about the risks of such heavy rotation, he added: "Yeah, that's the risk that you take."

Rosenior said the policy also helps bring players back to fitness, including Romeo Lavia.

"We are going into a period of games where, for example, Romeo Lavia can be really important because he has to play minutes,' said the Blues boss.

"We have to get him up to speed. Dario Essugo, we have to give him time on the pitch.

"(Lavia) is a top player, but you can't expect perfection from a player who's been out for four months.

"It's not just about your first 11 or your first 12 players to get us to where we want to be. The only way our players and our squad are going to help us achieve what I think is possible is for them to be sharp and ready.

"I would say it's not guaranteed that if you start your first 11, these games will come easier. And also the amount of games my squad have had in the last 18 months is the biggest in the world. So at some point I have to trust the group. They repaid my trust with the result tonight."

Chelsea next face Paris Saint-Germain in the UEFA Champions League on Wednesday.

Real Madrid eye Roberto De Zerbi as potential successor to Carlo Ancelotti