Ben Chilwell has been surprised by Mason Mount's work ethic since they became Chelsea teammates.

There were doubts the 22-year-old would continue his ascension after Thomas Tuchel replaced Frank Lampard at Stamford Bridge.

However, Mount has been excellent since the German arrived and Chillwell thinks the 'sky is the limit' for his Chelsea and England teammate.

"Before I came here me and Mase were close through the England set-up, but that was only in training and playing with him a few times a season," said Chilwell in a press conference prior to Tuesday's Champions League quarter-final second leg with Porto, in which they hold a 2-0 lead.

"Now training with him every day, I see how good he really is. It's not just his natural ability, but the fact he works very hard, he is very keen to learn all the time, and he is always doing extra work in the gym. He does everything he can to better himself.

"With the natural talent he has, his work-rate, the sky is the limit for him. Since I've come in until now, he has improved so much.

"If he keeps on doing what he is doing, scoring, assisting, staying humble, working hard, then he will be a great player for Chelsea and England for a long time."