Maro Itoje has warned England's rivals there is still more to come from Eddie Jones' side despite their impressive 2016 so far.
England are yet to lose a match since Jones took charge of the national team in November 2015, a run that has brought them Six Nations glory and a first series win in Australia.
Itoje is one of the new faces drafted in by Jones after their disappointing Rugby World Cup display, the 21-year-old impressing in roles across the back row.
The Saracens lock has enjoyed a great year with a Premiership and European Cup double to add to his international success, but he expects even more in the future with both sides.
"If anybody gets carried away at both Saracens and England the environment stops that from happening," he told The Telegraph.
"I don't think they have but, if it were to happen, the culture would stop it
"The most exciting thing is I don't think any of those two squads are anywhere near their potential. I think both teams have a lot more to give and show.
"If we continue to work hard, stay humble and have that hunger we will get better."
Itoje has been highlighted as a star of the future, but he says he has lots of improvements to make if he is to establish himself as a regular for club and country.
He added: "There are a lot of things I need to work on, trust me. But those kind of things are between me and the coach and I'd like to keep it that way.
"Obviously I'm nowhere near the finished article. I'm definitely not at my peak. I'm 21 and there are loads of things the coaches have highlighted to me, which I need to improve.
"The challenge for me now is to go back to my club for the rest of pre-season and work on those skills and areas I need to improve. Hopefully we'll see an improvement after the first couple of games."