Smalling was a regular for United last term - making 46 appearances in all competitions - but was left out of Gareth Southgate's squad for this summer's competition in Russia.
The 28-year-old has admitted that he was 'disappointed' to be left out of Southgate's squad, but is confident that United will see the benefit of the 'biggest summer break he has ever had'.
"Initially, it's obviously disappointment, because you want to be a part of big tournaments. I had to come to terms with that and I made the most of the biggest summer break I've had in my career and I'm feeling fresh and ready to go," Smalling told reporters.
"I'm feeling good. I went to Thailand and Vietnam. I made the most of it. And I can hopefully get a full pre-season, which I've not had in many years.
"I just want to follow on from the number of games I played last season, keep kicking on and helping the team, just making us play better together and hopefully win some trophies."
Smalling has featured in all three of United's pre-season matches this summer, which have brought draws against Club America, San Jose Earthquakes and AC Milan.